As implied, I'd say your mechanic is in CYA mode. I've used non Honda Dot3 fluid on 01 Civic now with over 210k miles and no fluid related issues, all original parts with the exception of pads and shoes.
Honda also said everyone should use Z1 too, which I bought into for ~165k mi. because of Honda's poor AT reliability record, until superseded. Since, gone with MaxLife in two Hondas also with no issues. And turns out Z1 was nothing special, in fact when it came to shear stability it was basically [censored].
As for PSF, used Bardahl H/A and now Prestone PSF for Honda/Acura also with no issues.
But your mechanic is protecting himself in case of a comeback issue. Can't really blame him as it's one variable he can eliminate.