I agree that if safety is the reason why you want them to keep it on, we are on the same page. I am not sure I would call it poor catching technique to take it off though. Usually players girls or boys migrate to taking it off at some point as they get older. I guess it's more a visual thing even though the new helmets are much better than the older style. MS ages you have a solid reason to leave it on but as I am sure you know, young ladies at that age have a mind of their own!
That's kind of the point - if the technique makes you less safe, it's poor technique by definition. Catching is inherently dangerous, we know that, but there's no reason to make it more so by deliberately unprotecting your head. Same reason you don't straddle the plate for a tag play or stick your glove into the swing zone.