@ shein,
I wouldn’t classify it as that. From what I have seen/heard in BP, the tzeirei is pronounced “a” as in “hey” you. Everything else is straight chasidish. Granted the Horowitz family did end up in litvish yeshivas where they were able to blossom in learning so it is possible they picked up some more “litvish” but the “a as in hey” havora was used by the Reb Moshe zt”l and Reb Lavi Yitzchok zt’l.