The honorific would’ve probably been “my Chancellor” if it had been about his political authority

In his case it was very much meant as dictator.

There was debate after Hindenburg died and he took his powers with the plebiscite (as well as chancellor) about what his title should be. He didn’t want to harken back to Kaiser per the previous Reich so they went with Fuhrer.

It had been used within the party before that but came into common usage as his title at that time.