Apple watch question

So a few months ago I got the new series 5 watch with the cellular data plan (since it becomes a world crisis if a couple people at work can't reach me first try)

Anyway, noticed a couple times now that when I'm on a call on my phone and get an iMessage text and possibly a regular text also, it won't come thru on my watch until I'm off the call. I've tried searching online but nothing really comes up for my issue. I was thinking that since I had the cellular on the watch that texts should come in to the watch while on a call and I'm pretty sure a couple times I have gotten a text on my watch while on a call. Am I right about that? If I am what settings should I look at to verify things are working?

I know the cellular works on the watch because I've texted before from the watch without my phone anywhere near me. I'm not too tech savvy anymore and certainly don't use my iPhone and watch to their fullest ability lol but it is nice to be able to use the watch without the phone near and check texts/calls while driving since I do get emergencies at work and would need to stop and text or call to take care of things.

Any input is appreciated.

(And please no apple/android crap, apple works for my needs and has for several years.)