I mean, you can't ban something because you assume it could become a threat, you gotta let it become a threat first.
The discussion used to be on how dugtrio affects the meta rather than how uncompetitive it is, but seeing how diglett works the same way and trapinch was thrown in for some reason they made things a bit messy.
Would it make any difference if they just banned diglett and trio, those two and trapinch or just the ability? i doubt it.
Anyway let's not go into complex bans again, that's both off topic and wasted time.
I'd also like to know what the council is trying to do atm, so i'll just wait for an in depth explanation