If you select a port rather than using Auto-Detect the flashing operation correctly uses the selected port. If you choose Upload Filesystem Image from the PIO menu it always uses Auto-Detect instead of using the selected port like the flashing operation does.
Can you file that as a bug in the platform that does that? E.g., https://github.com/platformio/platform-espressif32/issues/ if it’s for ESP32?
Done. It’s been like this for a long time and I just never got around to posting about it.