If that attachment is accurate, it sounds like the non-MLS teams in U15 in Socal will get MORE games against MLS Academy teams than they did when they were in DA. In DA at U14, they got 4 games against Galaxy and LAFC (two each) out of 28 games (assuming they played no MLS teams in the showcase). In other words, they only got a little over 14% of their games against MLS teams. Now they get 20% against MLS Academy teams according to the right side of the table in the attachment, or 8 out of 40. The rest of their games are against former DA teams that are not affiliated with an MLS team, which is the same as they had in DA.
Even if we assume the former DA clubs in Boys ECNL negotiated a similar 80/20 split so they could mostly play the other former DA teams (and I don't know if that is true), that still leaves them playing 20% of their games against the pre-existing Boys ECNL teams, many of whom in Socal were not even competitive against CSL Gold teams and SCDSL Flt 1 Championship teams.
So, it seems like both groups of non-MLS former DA teams may continue to mostly play other non-MLS DA teams for the majority of their games, but the ones in the MLS league play stronger teams for the rest of their games and the one in Boys ECNL play weaker teams for the rest of their games.