Medical POA question

I had an interesting event happen yesterday. I took my mom to a pulmonologist appointment. A doctor she has seen several times. As usual, there was a form to sign while in the waiting room. I had mom sign it- consent for treatment and to bill the insurance. She signed her first name and I had to prompt her to sign her last name. When I handed the form to the clerk, I casually mentioned that I might have to start signing it. And that I had MPOA and DPOA.

The clerk actually stopped what she was doing and called up the scanned MPOA on her monitor. Then made a point to tell me that the MPOA was checked as ‘in case of incapacity’. No one has ever questioned my authority to get them medical treatment before.

Anyone else have issues with this before? There’s a place at the bottom for anyone to sign for the patient if they can’t. It doesn’t say to hand over legal documents to say you can sign. I know I’ve signed for my children ( when they were minors) and for my parents in the ER before. I’ve also signed my parent’s names electronically at the PCP’s office before when I check them in. At the direction of the clerk there.