I have tracked the results for years and the games I saw, the DA teams usually lost/won to non-DA teams according to the expectations of YSR predictions. The only ones that seem skewed are LAFC and many of the MLS DA's around the country. LAFC should be even higher than they are in composite score and I think that is because they play their subs a lot and early on in the game against the lower level DA's. In fact, LAFC has sent their younger squad to play low level DA's and they still won easily. YSR doesn't know that, it just inputs the data. Had they sent their age appropriate team it would have been a massacre. As I have previously noted the disparities between mls and non mls da's outside California are even larger. So< i expect they are doing the same; they are playing their subs more frerquently and maybe sending younger squads against weaker teams. It's all just more proof that the non mls DA's were a poorly executed plan. Don't even get me started on ODP, what a cluster f***.
You are correct, ECNL seems to have a prestige advantage over the other leagues, especially on the girls' side but I only scout on the boys side and honestly, I follow players and teams not leagues and clubs. Club prestige and history means very little to me until it actually translates to real success. SCDSL copied CSL by having one primary place to play and that definitely helps scouting in practical terms. CSL sends out over 2000 premier guides to coaches and scouts and I think the other leagues will follow suit with print or online links to all those teams and players. But to me the promotion/relegation must be the difference in why a CSL team that is frequently regarded as inferior because of a stigma, frequently beats the top teams from the other leagues that claim superiority. Once again, huge difference between girls and boys regarding these leagues.