“Rebbetzin”:
“Over the years countless gedolim, Rosh Yeshiva, Admorim, Rabbonim, poskim have come to farbrengen of the Lubavitcher Rebbe, yechidus, dollar line, kos shel bracha…”
Many of them were Hasidic, of Hasidic background, or roots, like Reb Menashe Klein.
Yes, there were some non-Hasidic who at times had some contact, but it was limited. Some of them didn’t fully realize how much Lubavitch had changed under the last Rebbe, and how times had changed in general. When they thought of Lubavitch, they thought of a different Lubavitch of the past, before his reign. One such personality, a renowned Rosh Yeshiva, a great man, was considered like a ‘Chofetz Chaim’, so perhaps he was not aware or didn’t give credence to reports of changes due to his pietistic way of life, and went to be menachem aveil after Rebbetzin C.M. passed away. Nevertheless, the Litvishe world in general, especially as time went by and Lubavitch became more and more openly messianic, distanced itself more and more from it. When Rav Schach ztvk”l zy”a came out against Lubavitch that also made a big impression on that world. It is important to see what date such things occurred, if they occurred at all, and to examine the details and circumstances closely. If a Rosh Yeshiva visited in the 1940’s or 1950’s, it does not mean that he would have necessarily done so at a later date.
As for the claim that Rav Moshe Feinstein z”l, zy”a, ‘sought counsel by visiting the late Rebbe for yechidus’, if you Google Rav Moshe Feinstein yechidus, the first result will lead you to an article that explains it. Basically it says that Rav Moshe was asked by someone he worked with to be mesader kiddushin for his wedding in Crown Heights, which he did. Since he was there, right next to to the late Lubavitcher Rebbe, afterward they met for a while, discussing matters of Klal. The Rebbe asked Rav Moshe a sheila, which Rav Moshe answered. To make it sound like it was yechidus, like when a Hasid visits his Rebbe, is incorrect. Rav Moshe was not a Hasid of the Rebbe, and he was also older than him.