It's the built-in mac display that goes blank along with the external monitor. On my Intel 2019 MBP it was very slow (many seconds), on this new M3 it's much sh

It's the built-in mac display that goes blank along with the external monitor. On my Intel 2019 MBP it was very slow (many seconds), on this new M3 it's much shorter but still more than a decent Windows laptop which is almost instant.