Changing in a Hoyer lift?

Who is insisting, is this in a private home or in a facility?
If this is in a private home then sometimes necessity is the mother of invention, while I can't quite picture how this would work sometimes people use these kinds of hacks because they do work for them. Open backed wheelchair pants and toileting slings are both fairly common. I'm guessing that a tab brief is being used and that this is to do a quick change for someone who spends their day sitting up in a chair or wheelchair and that a thorough cleaning is done morning and night and if there is a bowel movement. Have they demonstrated this to you?
If this is in a facility I wonder if this is a time saving method invented by front line workers that senior staff are not aware of. Since you sound prepared to walk you have nothing to lose - definitely kick this up the chain of command in writing, all the way to your state's regulating body if nothing changes.

I can't fathom how you can do this. How do you get a diaper on?

I would demonstrate the proper way to do the change in bed and see if they are agreeable to it. Try to gently explain to them (so they don't get defensive) that it is much easier and safer to use the bed.

I have never heard of this, nor would I allow it. I am a Licensed Nursing Home Adminsitrator. I agree with you that is seems unsafe. You, as a worker and mandated reporter, do not have to perform this task if it feels unsafe. You should not be fired for it either. Please file a complaint with the state you live in. The department of health should investigate this as a safety issue. It also seems like an undiginfied way to change clothing. Clothing changes can be done while in bed.