So pre 2008 there may have been, but that is pretty irrelevant now.
I never heard of anything in my time during CF.
If a mortal leader wants to impose restrictions, well, that's a leadership decision and that's always the case. A commander could just as easily say no assassins or warriors (and one did limit the number of warriors he would induct as I recall)

If all the bard's songs did mental or physical damage, it would probably not be an issue.
So basically apocalyptic, which can be mental fire or ice, is the only one that I think falls into the quasi-magical realm, since how does a song manifest a ball fo ice or fire (and what icy or fiery doom is I don't even know, but it is those damage types, and the fact that it can immolate means there would have to be actual flame, not imagined. Maybe he spits out booze and it catches fire. Hell if I can possibly explain the ice one though.

All the other songs can easily fall within mental, except piercing and vibrato, but those are physical damage which you could attribute to soundwaves.
(Convincingly, of course not, but this is a fantasy game after all)

My bigger problem with a bard's realism was that he could sing a verse of song, and play an instrument (there are a lot of people playing a lute with just one hand), while swinging a sword, parrying and dodging and all that. But again, fantasy again, so what the hell. And I loved bards too much to want them to go away.

I would just say it was a pretty foolish distinction for it to ever have been made.
But probably because village bards greatly enhance the villagers around them, they added restrictions initially.
Those restrictions were just shittily implemented in the first place. Bard songs are either magic or not, it's a pretty clear line.
To allow them at all into the village means they are not.

If Imms want to say they have to be bardy, so be it. But by that same token they should have to be regardless of cabal.