I wonder if a tune or two, like many other things, can undergo change. I have experienced myself the subtle lyric changes that have sometimes been made to some songs of recent popular singer/songwriters even though the dots, lyrics, and chords are written down. Can this happen to some of the traditional tunes we have had for years?

Withington Warbler (how is Withington these days BTW?)

All the time.

The aforementioned 'Hardcore English' features two pages of various versions of Speed The Plough;

Matt Seattle's book 'The Morpeth Rant' has multiple versions of the title tune;

Powderkegs Morris play The Rochdale Cocoanut Dance subtly different from our good friends Dead Horse Morris, and even further away from the Bellowhead version;

and it may (gasp) even be that the very tune books that Les has created for The Beech sessions are part of that process, if (and I've never looked at them the books so don't know) there's a variation in there that someone adopted and has been enshrined in the notation.

It's happening all the time, and it's a good thing.