As I’ve demonstrated and pointed out, if R’ Dovid holds it’s l’chatchila, he’s not disagreeing with R’ Forst, he’s disagreeing with his father. His father clearly held that it’s not. (I use the term “l’chatchila” to mean when there is no “shaas had’chak”.)
BTW, I did hear from someone I know who was in R’ Dovid’s house and he was served only cholov yisroel. He didn’t know if there was also cholov stam in the house.