Here is the deal. The yeshivshe velt thinks they are making a stand for the Torah of Eruvin. This is more than just a question of halachic decision. The R”Y organized a meeting (Please tell me if you know this to be true or false. Third hand information. I trust the second hand’s reporting, but not his grasp.) to discuss Meseches Eruvin in concept [Among other things. The point was to be above the table about their differences.] but the major matirim didn’t show.
According to Rav Moshe himself, one can rely on (at least some of) the poskim who approve of the Eruv. (Even though they are wrong on the matter.) But it doesn’t change this issue. The Yeshivaliet will not approve of an Eruv here even if the metzius would change. In their eyes, the whole business is a callous approach toward Torah and Mitzvos. It strikes too close to the core of what it means to be a Ben Torah in a Yeshiva, to ever gain acceptance.
To the OP – This must be the fifth time I wrote this response to you. I think you got this answer in real life.