Thank you CS for the source. That refutes my claim lo tisgodedu definitely doesn’t apply here; it also refutes my claim that Lubavitchers tend to ignore minhag hamakom. I guess I had drawn incorrect conclusions from Lubavitchers I had met who weren’t necessarily acting correctly.
I concede that we can’t say Joseph’s argument is baseless anymore. However, I will still say that we (Litvaks) clearly don’t posken this way in regards to Brooklyn. Kiryas Yoel could very well be different; I’m not sure.