I work in a way that requires me to focus for periods of time.
I find that booking a time that is mutually convenient (even for a short conversation) is preferable to possibly interrupting or being interrupted.
It means I can give my full attention to the exchange and make it a priority. Call me when I'm in the middle of something and you'll get less attention because my mind will still be on the task I was doing.
There's no part of my day that isn't busy (work, team, manager, personal).
Personally, for casual, non-priority conversations, I rather async mechanisms (messaging) be used first, and then if something develops that warrants a "face to face" conversation, we prioritise that time.
I think if someone has said "please book time with me" they have already made you a priority to talk to because they are giving you the most valuable resource a person has.