The answer turns out to be that old dell machines shipped some shitty avatar software (along with lots of other stuff) that defaulted to on. The lawyer is probably using an ancient dell computer with this software and hasn't used video chat on it before this.
This is extra hostile, because it's separate from whatever video chat application they were using - so it would have been harder to know about and turn off.
As an aside, Microsoft fought in court to force OEMs to not install this crap alongside Windows (reasonably since it was damaging their brand and making the machines less secure), but they lost. Another reason why the macOS model is better for users. OS companies should make their own hardware.