Answer

You’d have to ask them.
I actually can understand it. There are some unconventional positions there on various issues, and they’re not comfortable with that.
In the past, when I published the Middah Tovah sheets on the hermeneutical principles, which is a completely non-charged Talmudic-analytic topic, there was still a yeshiva that refused to allow them in (and I assume that was true in the other yeshivot as well). There really was no substantive reason there, only perhaps a stylistic one (a somewhat foreign-academic language. Really very minor).