Who's claiming that pre-Cannon Xiang Qi closely resembles Chaturanga? Perhaps there really is a Charles Gillman and for some reason I cannot see his comments! For myself I acknowledged that the differences were (a) considerable betwen Chaturanga and any kind of Xiang Qi; (b) considerable between Chaturanga and FIDE Chess; and (c) relatively slight between pre- and post-Cannon Xiang Qi. I simply added that it didn't follow that two considerable changes going west - Xiang Qi to Chaturanga to FIDE Chess - and a slight change in China were any more likely than one considerable change going west - Chaturanga to FIDE Chess - and one going east - Chaturanga to Xiang Qi.
	Saying that the General has 'only 1 counselor and 1 minister on each side' (perhaps that's where the rogue L came from) is puzzling, as that - on the basis that 1 of a piece each side of the General means 2 of that piece in the entire army - is what Xiang Qi still has and therefore there is nothing for it to be 'only' compared to. Or are you saying that there was only one short-range piece on each side, a one-step one on one and a two-step one on the other? If so, this is not a game that appears widely known of based on previous comments.
	I would not say that Chaturanga looks more 'modern' than any kind of Xiang Qi, only that it looks simpler. Why should 8 more pieces (4 aside) be any greater a sign of a more recent game than 26 more positions for them to occupy?
	The first 8x8 game certainly did not have '2 minister and 2 counselors'. It did have two Elephants - the Elephant=Minister pun was specific to China and did not work anywhere else - but there was one Counsellor with two Ls, not two with one each. That one 1-step piece does not fit 8 files as well as two fit 9 files does indeed mean that the latter case had 'no improvement needed', but it does not follow that the game not requiring improvement is the older one. It could equally be argued that the one not requiring improvement had already been improved a lot from some predecessor, and the one still needing improvement had not - and perhaps was that predecessor.
	The point about which change of board is more likely is, as far as I understand, unaffected by any known timeline. Are you saying that there was a time when Xiang Qi was known to exist and Chaturanga known not to? Otherwise what matters is which change seems more natural. Chaturanga's board with 8x8 squares or 9x9 corners had already been long in existence for the older game of Ashtapada. It is easy to imagine versions of this being made as two half-boards, each with 8x4 squares or, as a result of repeating one boundary, 9x5 corners. This is then easy to turn into the Xiang Qi board, complete with something that could be interpreted as the River. It seems far less likely that the River would be invented spontaneously and the Indians then 'take out the river', deliberately or accidentally.
	Your conclusion that 'games that are based on another game, generally will finish its development at a later date than its predecessor' sheds no light on anything. Chess with modern long-range Queens and Bishops was already only 'based on' an 8x8 game that had been in existence for many centuries, regardless of what that earlier game was in turn based on.