They are from artillery and had always to take care of their "Geschütz A(nton)-F(ritz)Why they should change their habit? Even in Stug units you can read " An die Geschütze"for entering up.
I would limit it to Pak, Flak, Mörser and Geschütz for the rest of guns inc. SPG.
Regards from Vienna
Visit our modelling show "Go Modelling" in Military Museum in Vienna at 10/11th march 2018