Is this rude?

[BlueBlazerBlack]

Is it rude to call someone while you are in the middle of a different activity that requires you to focus on other things and prop up your phone and be out of shot for part of the conversation?
I have a friend who does this and it drives me crazy. I feel like this is taking multi-tasking too far. It is distracting, it feels disrespectful and makes it hard to sustain the conversation, but they seem to think it's fine because they are a busy person and don't have time to just sit and talk.

YANBU - it is annoying and you shouldn't call someone if you need to do something else at the same time.
YABU - it's fine to do other activities while you are facetiming.

I have a sensitive streak so happy to accept I may be unreasonable.

I don't want to specify the activity as it could be outing...

I do technical support on phones for work, there's one guy in particular who will ALWAYS be eating every time he calls, and only manages to spit a word out between chewing & swallowing. It's vile.
Another who will call for support & make me the least important person in the phone call between me, him and whoever else he's having a conversation with in person at the other end. Every time.