I think people overthink this, and I think I overthought it when I just did it this week. The fact is that when you fire people, most of them are going to be upset, and they'll find something to rationalize that emotion no matter what you do. If you have a face-to-face, they'll say "Can you believe he was mocking us by wearing his ball cap, or his old tennis shoes, or those jeans he wore the same day he hired all of us, or that polo with the company logo on it like the company hasn't already been besmirched? How disrespectful!" or they'll just completely fabricate something like "Wow, he was so aloof in that meeting, what a mean guy".
What it really comes down to is that most people are going to look for "facts" that support their emotional perspective, not emotions that are congruent with the factual perspective.
The pre-recorded call firings are done that way to make sure the phrasing is perfect. Most likely the lawyer has already written the script and they do several takes to perfect the firing executive's inflection, tone, etc. I don't think this is objectively worse than firing someone in person or via e-mail either.
For the record, the employee I fired stated that the firing was "classless and vile" despite the inclusion of a generous and completely optional severance package, an immaculately respectful email that politely informed her the position was being eliminated and stated that we hoped we'd work together in the future, and so forth. It was honestly one of the classiest firings in which I've been involved, but like I said, to the fired person, there's always a grudge to find if they want to find one, and she wanted to find one. Her grudge is that I didn't "give the customary notice period" for a firing, which afaik absolutely doesn't exist anywhere except in the few cases that fall under the WARN act (under which companies are entitled to pay a severance equal to the legally-mandated notice period in lieu of notice).