In case future readers search for this scenario...
A former coworker, who is now widowed and in her 70s, was able to have wheelchair service requested at booking for a non-physical reason. I suppose I'd call it anxiety? Is it okay to call it a mental disability?
Her husband of 40+ years always took care of things inside and outside of home and she never needed/wanted to learn how to do things on her own. Her daughter lives in another state and my friend now goes out to Texas for a month-long stay every year. If she had to do any part of the travel process alone - of getting to the airport, checking-in, going through security, finding the gate/connecting gate, finding the airport exit, etc - she just plain wouldn't leave home. Actually, I remember now, her neighbor was allowed to accompany her and the wheelchair attendant through security and airside at SJC.