Here’s what Signal says: https://signal.org/blog/contact-discovery/

Signal knows all of their users’ phone numbers.

Only the hash of your phone number.

Genuine question, how precise do you need the time to be? Maybe you actually need precise readings for something. I figured that “on the 5 min marker”, “slightly before/behind the 5 min marker” and “in the middle of two 5 min markers” is precise enough for me. And I see a hand at these positions faster than reading numbers.

I think for precise readings (eg. entering the time I start working), the speed is the same for me, but obviously I didn’t test this.

I also think looking at the time but a few seconds later still not knowing what time it is happens less on an analog clock.

I don’t know how much personal preference influences this though.