Maybe it's not that simple - there probably is some impact of ratings and I guess that's what Evaristo is interested in: how team ratings affect the outcome of certain game events, situations or even players abilities during the match.
I would say that all situations are individual skill vs another individual skill.
It has been observed that 3pt shooting % is better when the shooter is guarded by some really poor OD player (OD 1-3) compared to shooting % of unguarded shots (where the shooter is free to shoot). The likely reason is that when a shot is unguarded, the team OD rating is taken into account (instead of the "missing" individual skill, since there is no defender to guard the shooter) which is usually higher than 1-3. Probably GE always needs an OD value to match against the shooting abilities of the attacker.
Otherwise, all unguarded shots would be in. Which is not the case.
This is one instance of situation that is not decided by individual matchup only - in this case, JS/JR of the shooter versus OD of the defender (not to mention the possible impact of the quality of pass to the shooter).
So it's possible to assume that team ratings affect at least some game events. Maybe a flow rating gives some coefficient to all players considering quality of their passing, handling the ball, the possibility of commiting a turnover etc.
This probable impact of ratings could explain why the teams with specially designed players (for instance, a player with low IS and high passing/ID/RB/SB that plays as PG in attack and PF/C in defense) sometimes struggle at the higher levels: their team ratings can be significantly lower than those of "ordinary" teams of the same strength.
For instance, that mentioned custom player will not count towards team RB rating, because he is set as PG for the game - and only rebounding ability of C, PF and a bit of SF are counted in RB ratings. So this team's RB rating will be lower which may affect their rebounding ability in general.
To be honest you made a very good point here, I have not analysed game engine in such depths. I want to thank you for such good analysis, even though it's more speculation and assumptions, but it actually would make sense.
Do you know how important passing is for PF/C, from what I understand they don't contribute to team's flow ranking?