That's a fair point and good advice, however the full quote was "Sorry, I'm in the middle of something important. Can you come back at lunch time?", which can then start being a full conversation to find a time that fits both of you. I think a good way to respect other people time is to use asynchronous means of communication as long as what you ask isn't urgent.

I tend to use slack this way. Writing out my thought process helps to clarify things, even if I don't ever hit the send button. And if I do hit send, then it gives a good sense of what has been done, and how.