It probably depends on the size of the state. We have huge compulsory numbers so the easiest way to do it is just do the sessions by age, if you have a big team, you'll be there all weekend. But otherwise, fitting together the number and size of teams would get pretty complicated, it's more straightforward to just divide. We have the same judges all weekend so team scores are just calculated at the end.
But other states are small enough to have their entire states in one weekend, all levels. And there are others in between. At the higher levels we do have a few mixed level weekends, but usually it's set up so the lower level goes first one day, then the higher levels. We don't have any levels or state meets where a session is mixed as far as what levels are within the session (even level 10s have their own sessions) but there are multiple age groups in every session. Usually three age groups per compulsory session (90ish kids total, max 96, three age groups around 32).
As far as the original question, if the judges write on a scorecard, usually there is a sticker on it with the child's name, gym, and age group for that meet (could say 8 years old, could say Jr A or B, or whatever). I've been informed on this board that in some places the judges use a roster to track the order - I have never seen just a roster used with no cards at any meet I've traveled to anywhere in the country, so I can't say whether those are set up to provide that information. If you're asking whether the judges care or even look at that sticker, not really, unless they're curious about something for some reason.