As I recall, Michael Gill himself didn't rate the tune section at all... His advice was always to "Listen, listen, listen"
yes of course listening is important and yes the tune section has limitations,and is not to be taken as always 100 percent accurate

but not everything is as black and white, as in the world of michael gill
accurate tune sheet music can be useful for tunes that have been forgotten,
here is an example
I remember the fiddler Paddy Cronin saying that he used to go through
O Neills 1001 to bring tunes back into the general repertoire
Paddy Cronin had no problem occasionally using sheet music