I reckon I can give you 'full marks' so far.
Seems you have pretty much arrived at the same conclusions as I did several years ago.
The Crowan scenario is certainly interesting and is one (different Wills and different Parishes) that I have seen before on a number of occasions.
There were certainly Phillips families at and around Crowan but the question is - did John Phillips come from Zennor and have associations at Crowan
or was he originally from Crowan and settled in Zennor.
Crowan PR's and BT's do not, from what I have seen, help us very much here so we need to tread warily and leave open all possibilities.
I will throw in a few things here for your perusal:-
Zennor PR's show the following baptism:-
__hn son of Matthew PHILLIP December 1607
The name is probably 'John' but I would suggest it unlikely that it is the man who married Joane Row as that marriage, to my reckoning, had to be sometime before 1625.
It does, however, show that the Phillips family was involved in Zennor at least that far back.
Matthew Phillips left a Will in 1628 at Zennor in which he named son Thomas (with three children).
A deposition regarding this Will was signed by Matthew's son, James.
From my previous research I had determined that Matthew also had a daughter Phillippa who married William BISHOP and that the John bp. at Zennor in 1607 was his son.
This would mean that the 'John PHILLIPS' as the subject of this thread is of a different, but probably related family.
And here things become even more interesting.
James PHILLIPS left a Will in 1646.
I believe this James to be the son of Matthew, particularly given that he had a son named Matthew.
It is also likely that this is the same James Phillips who was hanged by Cromwell.
We can debate that part of things later on - but for now, the interesting point is that, in his Will, this James left 'two shillings and ten pence' to the poor of Phillack.
I found a baptism for a James s/o Matthew Phillips at Phillack in the IGI some years ago (25th March 1600).
But I now have reason to think that date is incorrect.
I will try to outline that part of things very soon but first have to say that my previous research indicated that the name 'Matthew Phillips' did not resurface at Phillack until 1776.
Here is what I can find now that 'may be' a possible connection and is taken from the Transcript of the Phillack Parish Register Online:-
Phillack Baptisms
Joane Phillippe d/o James bp. 12th August 1580
John Phillippe s/o James bp. 25th February 1582
Katheryn Philip d/o James bp. 13th March 1583
Thomas Phillippe s/o James bp. 26th September 1585
Agnes Phillippe d/o James bp. 6th March 1587
Priscilla Phillippe d/o James bp. 1st January 1591
Pascha Phillip d/o James bp. 17th Novmember 1593
Anne Phillipe d/o James bp. 12th October 1595
Pascus Phillip d/o James bp. 15th April 1598
JAMES PHILIP s/o MATTHEW bp. 21st March 1599
The next mention of this family in Phillack Baptisms is not until 1620 when Anna d/o Gregorie Phillipps (Rector) is baptised.
Phillack Marriages:-
15th November 1579
James PHILLIPPE m. Katheryn, d. of Thomas MARTEN
Phillack Burials 1577-
6th April 1585 Thomas Marten
27th November 1594 Priscilla d/o James PHILLIPPE
30th August 1602 James Philips
4th February 1607 Thomas Phelyp
6th March 1617 Anne d/o James Phillipp
Next Burial is in 1624 for a daughter of Gregorie Phillips.
The fact that James Phillips left money to the poor of Phillack indicates some connection there and I think it probable that it was he who was baptised there in 1599.
Conclusions from the above (combined with your own note) would be:-
The Crowan connection is certainly a strong possibility, especially given the bequest to the poor of that Parish.
James s/o of Matthew is 'almost' certainly the person baptised at Phillack in 1599. (ref. bequest to Phillack poor)
The family of Matthew Phillips has relocated to Zennor sometime very soon after 1600.
The James Phillips with children bp. at Phillack is 'very likely' a brother to Matthew.
So - is the John Phillips of the 1654 Will the man baptised at Phillack in 1582.
It would, because of his age, seem to be less than likely (but not impossible) if he was the man who married Joane Row.
Whichever way we look at it it would seem that John and Matthew Phillips were most certainly related - but not, I think, as brothers.
The ROW side is also interesting.
Richard Row (Will of 1637) is, I believe, the man who married Agnes Walcomb at Zennor in 1617.
Whilst I have, so far, been unable to determine the fate of Agnes I believe that Richard had at least one other sibling.
And this was Margery Row who married a Roger CHRISTOPHER sometime before 1620 and, presumably at Zennor.
I think we need to find out if there are any records available for Crowan (in any form) prior to about 1676 so that we might have a 'reasonable' chance of proving some of these connections.
Other than that we need to pursue every Will relating to the combined Parishes to see if something might be mentioned to help us.
I think I will leave this for now and give us all time to refresh.
Reckon it will also give you a little more to ponder about.
Anyone else who might have something to add here - PLEASE DO.