Not entirely true. Even on my M1 Air, the power consumption approximately doubles when I'm on a Zoom call. Not that it struggles, but it does warm up and runs through a good chunk of battery percentage over the course of an hourlong call.
I don't remember which Retina MacBook she has, but I do recall that back when she was using it as her primary machine it would straight up stop working if it was in a warm environment and trying to do a zoom call. (She's a clinician who uses zoom a lot).
Strange. I've been told if you record meetings and use virtual backgrounds and such, that can up the CPU usage, but if you don't it works just fine. Like I said, I had no problems with Zoom with my 2.5 hour lecture. Here was my setup on my 2017 m3:
1. Running PowerPoint 2016 in presenter mode. Main screen with my notes and next slide on my MacBook screen, and actual presentation on external screen (which was actually a 2010 iMac in Target Display Mode).
2. Running Zoom with screen sharing, sharing the external screen (iMac) over Zoom.
Yeah, battery life wasn't great, but the machine didn't struggle otherwise. FWIW, I do have 16 GB RAM though, if that makes a difference. PowerPoint crashed once in that 2.5 hours, but I blame PowerPoint for that. I'm using an old version and I've found PowerPoint can occasionally be flaky with large presentations. Zoom never crashed during that time, and the machine never became sluggish (or at least never became any more sluggish than it usually was with that Core m3).
