Precisely, flirting signals to someone else that you’re potentially attracted to them.
If they’ve written you off as a potential romantic partner for whatever reason (they assume you’d never be interested, they thought you had a partner, they thought you were only ever going to be just friends, etc), then that signal can cause them to start considering you as a romantic option.
Take your pet for a walk.
Personally I find biphasic sleep pretty normal and easy to do when I’m working a job in a timezone that’s behind mine by a few hours.
Go to bed at 12:30, sleep 4.5 hrs til 5:00, wake up with the cat at dawn, take them outside and enjoy the morning tranquility for a bit, go back to bed at 6, sleep til 9, get up to start my job at 10 or 11.
I don’t do it when I have to be up early though, I both always struggle to go to bed early, and I find waking up and being up in the middle middle of the night, to feel more stressful than doing it at dawn.