Feif Un: And it may very well be that Rav Lau is well respected personally by the Viznitzer Rebbe, but he can not stand together due to his position. Similar to someone not wanting to join with Rav Elyashiv ZT’L due to him having been a Zionist Dayan, without taking away from his Gadlus. I imagine had Rav Elyashiv spoken at a Siyum HaShas, there would be the same reaction.
That being said, it is a removal of Achdus from what could have been. Too bad.