I am currently using Jaguar pie - non-treble rom along with boot image is from xtended pie- non-treble rom as it because it supports spectrum profiles and thus pubg is better with gaming profile set on spectrum.
Never faced any such issues with Treble or Non Treble ROMs. Yes, there are specific ROMs or a single version of some ROM may end up having any bug or issues but it would be unfair to term entire TREE as problematic !!
Couple of weeks ago, I was with Pixel Exp 10, and that particular release was having this said issue. I have just updated to the latest release of PE10, so will check in next few weeks if the issue is still there or not. But certainly I can confirm, tried many Treble Oreo & Pie, I personally never faced any issues in those regarding Voice call issues.