hello: BTW, according to this Maharit (and common sense experience), the practice in Israel of making cheese bourekas triangular is ineffective.
You would have to prove that the issur also applies to other things aside for bread. Because as we have mentioned, “ki al halechem yichye haadam”, means that I would eat bread with anything, meat or dairy, and therefore it’s “karov levadai” that I will eat it with the wrong foods.
This doesn’t apply to borakas unless you can prove that borekas are eaten with (directly, it’s not enough in the same meal) meat and dairy.
Aside for that, if you add in the Rashba, that you just have to be questionable of the status of something in order for the siman to be good enough, I think pretty much anyone who doesn’t know the proper shape of borekas makes sure to check inside first.
And you also have the Pri Megadim in Siftei Da’as that mentions that forsure if you see the Shuman on the bread its considered a good siman. Being that most borekas have cheese oozing out of them, the chumras of the rabbinate is probably for naught (if you add up all the aforementioned reasons to be meikel.)