The old PGE exaggerate things. They are not "exclusively carnivore", however they are not allowed to cut, pluck, cut, harvest or otherwise gather vegetals (including timber for building things and fruits and vegetables for eating).
However, if somebody else already did it, then it's fair game. If a Bosmer needs a tree cut, he'll hire an Imperial to do so.
I dont quite think it works like that, either. That would be a
pretty grave loophole exploit.
I just think the Green Pact is restricte dto valenwood Forrest, and hence for all purpsoes doesnt apply to Bosmer in Morrowind and Cyrodiil.
And of course, in Morrowind, House Telvanni seems to be made 90% made up of Bosmer on the lower ranks anyways, and at least for those I indeed dont think religious orthodoxy is a great concern...