"but where group singing is involved,"

I don't think we do that in the UK either. And personally, I'm glad for it too. I want to hear an individual singer. Including the beautifully delicately ornamented Irish song from one lady, which holds the entire pub (including the ba regulars) in silent thrall. The rich hearty shanty, with call and response from the gent (who actually used to be a fisherman). The well crafted harmonies of a couple who regularly play and sing together. I could go on and on. Without this variety and colour, all sessions would seems the same to me. In the sessions I go to, there are chorus songs (I did Alison Gross last time) and people *pick-up* the chorus. And there are old favourites that never fail to get everyone joining in. So all the options are there, but there's no prescription.

It may work for you, but as I say - the notion of a one size fits all book that everyone sings the same songs from all together, reminds me of 'mass-processed' folk music (rather than the more traditionally processed stuff). And for my own part, I'm thoroughly glad that we don't have it here.