"having only heard one example of a song; typically a recorded arrangement made by their favourite professional performer. As a result, they are likely to assume that there is only one form of it, "

A funny story from my SCA days:

'they' had learnt to dance 'the bear dance' to a recording pirated to Aust from the US on a cassette tape of a particular recorded version of a tune called 'the bear dance' - it even allegedly had (ancient!) words that were sung while dancing.

Now my limited research (pre-internet) had shown that this was a fairly ubiquitous tune in many variants and cultures across large parts of Europe - I even accidentally found a tune on a 'classical' CD which was of 'folk tunes' - but the tune was clearly a close variant!

Now there was a local 'folk music group' who did a lot of 'old, trad' tunes, and they knew several versions, and were present at a public event - they were asked 'did they know "the bear dance tune" so we can dance to it - we know it well!' - so they played the variant they normally played, only to be soundly abused 'that they were playing it wrong!'

I was present, and also later heard the story from the band's point...

:-)

I'm not making this up, you know!