“Hm…icould there be a mcholokes on this?”
I believe what your teacher meant is that you don’t fully convert to the minhag hamakom when you’re just visiting. Eg, you still wrap tefilling privately when visiting. However, were I to permanently move to Jerusalem, I might have to stop wrapping altogether on account of minhag hamakom.
The case of not publicly going against minhag hamakom is not actually about changing your minhag to that of the place. Rather, it’s that you don’t want to be over on the issur of lo tisgodedu. These are technically separate, albeit related, concepts.