Yeah, but as MT has said, getting a coach to do that is really hard. If the keeper is already playing 1/2 the games full time in goal (or is playing 1/2 a game in goal), getting them field time is hard because the coach will already feel the need to give the benchers some time (who have had none) v. the keeper (who may have already had a lot, just not on the field). I would be happy with just some field time and a team that also teaches to play the backpass so his feet get some work. But in an ideal world, yes absolutely.
Which is why I don't understand why his old club treated him the way they did. O.k....let's assume even arguendo the new keeper has tons of potential and more than my son has long term....if he's your golden boy, don't you want to give him some time on the field for the development of his footskills and sticks around long term? Don't you want for the sake of his confidence to take him out at the half when the team is losing 4-0 and the outcome isn't at issue? Don't you want someone else ready to go given how often kids at this age get sick or injured and shouldn't you celebrate that you have the great luxury of having 2 instead of trying to pit them against each other? The only explanation that we can think of is that when the kid was recruited he was promised a starring role, they didn't anticipate the jump my son was able to make in commanding the backpass and blocking with futsal and his trainer over the winter, and he embarassed them (or the other keeper's family) so they didn't want to give him time in goal afterwards and risk it happening again. My son said after the first game (where he only let in the PK) he got a vibe they were angry with him...I didn't see that but they certainly weren't congratulating him on a great outing even when he was fouled hard with a kick to the groin and no foul was called but played on.
p.s. the other thing that's just not cool is they have a no cut policy for returning players on the younger end....if you pay your fee on time, you've earned your spot on the roster...but that doesn't guarantee that they'll give you play time....the email I got was basically we know you've been looking at our competitor, you'll probably be happier elsewhere considering your son is very demanding about his playtime (he didn't make demands...he asked his coach why he wasn't put in and was told the other kid forgot his field shirt which turned out not to be true), you can stay but we don't intend to give him playtime, if you can't find a team at this late date he's welcome to keep coming to GK practice for a fee but here's your deposit back.