Can't speak with any authority on R22 etc. I'm X-Navy (Royal) & have done full downs in Gazelles & Seakings! A must in terms of experience!
However since going 'civvy' haven't been allowed to do one at all!
I feel this is V.Bad. I fly Police machines & the places we put ourselves makes me think the more practice the better!
Unfortunately commercial operators will undertake practices not required by law, especially when they pose a risk to airframes!
If you can talk someone into doing them...DO THEM!!