How can I use Face ID with Assistive Access on iPhone?

Ok I'm an idiot (kind of). What's different is that, unlike in regular mode, in AA mode there are no animated graphics indicating that Face ID is trying to recognize you; it just immediately presents you with the Passcode option if it doesn't recognize your face. So it was working all along and I just didn't realize it (my mom was taking a nap, so I couldn't test it with her until she woke up). Hopefully this will be helpful to anyone who has this issue in the future.

Thank you for the reply. I really appreciate any help I can get. Maybe I'm just dense, but I read and reread those instructions, both before I posted and after I got your reply, and I still don't know how to make it work. One problem is that it says, "To make changes to the device passcode, Face ID, or Touch ID, tap Change Security Settings." But I don't see "Change Security Settings" anywhere. Where am I supposed to tap that?

Edit: Maybe I have to start all over and go through the Assistive Access setup again from the start. Maybe I missed something in the setup that you can't change once it's set up. There was just so much customization that we did in setting it up that I hate to have to start all over again.

So, for the record, I used Reset Assistive Access to start all over from the beginning and went through the whole setup again. Eventually I got to this screen:

Since it said "Face ID is ready and Passcode is set", I thought I was good, so I clicked Continue. But when I finished the AA setup I was right back where I started with Face ID not working in Assistive Access mode. So I reset again, and setup again, but this time when I got to the above screen I clicked Change Security Settings. All that did was take me out of Assistive Access setup into the regular security settings screen, which had absolutely nothing helpful since Face ID was already set up and working in regular mode.

So, if anyone has ever successfully gotten Face ID to work to unlock the phone while in Assistive Access mode, I'd really love to hear how you did it! 🤯