using iPhone as webcam via Camo Studio, or EpochCam both produce a blurred background in Zoom

I know what you're thinking: don't forget to turn off your blur background filter.  The crazy thing is: this is a fresh install of Zoom and the background filters aren't even installed, let alone enabled.

Here's what I've tried:

As stated in the title, I've used both a default install of Camo Studio as well as EpochCam and both produce the same result.  When I look at the camera output in Camo Studio, the background is crystal clear, however at the same time it's blurred on Zoom.  I've also tried using OBS as an intermediate, to see if the problem is between Camo Studio and Zoom.  However this produces a clear background in OBS and the blurry one remains in Zoom.  What's interesting is I've tried adding a window to the camera feed in OBS and when it arrives on Zoom this too is blurred.

I've also tried capturing the output from all of the above in Quicktime.  This produces video with a clear background.

At this point I'm totally scratching my head, the only place I can find where this effect is present in in Zoom itself.  Here's the equipment I'm attempting this on:

M1 Mac mini - MacOS 12.0.1

Iphone 11 - IOS 15.2

Apple Silicon version of Zoom - 5.8.6 (2879)