Scrump - - you wrote 'Beginners also usually don't know that many chords, so an Am7 or D9 or the like is a complete mystery.
If you see a chord like that, that you don't know, try substituting the 'plain' chord instead, e.g. Am instead of Am7, just for the purpose of learning the song. It won't sound exactly the same, but it will usually do to get you started.'

The original question was about being asked for the chords. If the beginner / novice / expert had the chords in front of them they wouldn't be asking for them – would they?

It was Bee who said the first part "Beginners... mystery". I was just giving some advice on that point, and trying to explain that if someone saw chords in a book or was given them by a Mudcatter in response to a request, they could try that approach I suggested. I went on to say:

Then if you want to you can look up the chords you don't know, and work those in as well. It's a good way to expand your chord 'repertoire' - and some of these chords are easy to play anyway.

If I'm asked to supply chords for a song, I try to keep it simple, on the basis that the person asking for them is probably a beginner or not very experienced. So I'll try to provide chords that give the bare bones of the accompaniment, rather than every nuance that you might hear by a good player. That will come with experience, and you can work up to that.

What I was trying to say, was that if I give someone chords to a song at their request, I will try to just provide basic chords that fit the song (as others have said, there is usually more than one set of chords that will 'fit') - which may not be exactly how I or anyone else might play it, but allows the person to have a passable stab at accompanying the song. It's up mto them if they want to add to it and embellish it with passing chords, etc. In general I can't know their ability and have to guess from the way they request it. I would normally assume the requester is a beginner or not very advanced player, or they wouldn't ask (but maybe that assumption is wrong!)

I realise that some requests are much more advanced, and I wouldn't presume to answer them, but leave it to an expert, e.g. if someone requested the tuning/chords to Canadee-i-o by Nic Jones - I wouldn't be able to do that as I can't play in that tuning (whatever it is).

I'm not sure if that addresses your point above, or not! I wasn't quite clear wht you were getting at?