The root issue here is that if the founder and general superior of the order wanted exclusive use of the “extra”ordinary form of the mass used by his friars, why should anyone care (have a problem)?
In other words, it should be perfectly fine for an order to exclusively use the extraordinary form. I suppose one could quibble with the concept of it having been “imposed”, but what if the use of the Tridentine Rite is considered a charism of their order and the prospective members of the order are well aware and join knowing this, in fact wanting this for their vocation? Therefore it’s use is not imposed since the men are joining by their own volition - it would only be imposed if someone was forcing them to join.
I don’t see why anyone from “the outside” would need to disturb this, in other words as you put it “the sources of angst are outside of the community...”
But that directly contradicts what the Order, itself, says:
It is our duty to respond, with knowledge and in conscience, that in reality, Fr. Stefano not only has never imposed on all the F.I. communities the use—much less the exclusive use—of the Vetus Ordo, but he does not even want it to become the exclusive use, and he has personally given the example, celebrating everywhere according to the one and the other Ordo.
So if the Order says that the founder and superior did not impose this and a reporter says he did, who does one believe?