While your question itself is good, it's unfortunately quite likely that the recruiters won't actually know the answer. So their answer isn't a good signal.
Separately, in larger companies, there will be significant variance between the onboarding process of teams/orgs.
Sure. Recruiters wont know the answers to a lot of questions. Especially things that are not talked about often or focused on at the company. If a company is proud of their internal training program they would highlight that to potential employees and anything a recruiter can use to sell the company they will.
It's true that a recruiter might not know about a companies training program and that program may exist and actually be good. But its much more likely they wont know because one either doesnt exist or isnt formalized at all and isnt a focus for the company.
Separately, in larger companies, there will be significant variance between the onboarding process of teams/orgs.