Really?
😱 I'd think that a science professor a person works for would have a better perception of that person's knowledge and capabilities in the sciences than a professor who teaches a class that person is in with 20-50 other students.
I asked my boss to write a LOR for me and she too is a science professor but I have not taken any of her classes. She and I did research together and wrote papers together. I'm very certain she has a better awareness of my knowledge and skills in the sciences than any science professor I've had as an undergrad.
I think admins should take a better look at each applicant's relationship with his/her professor/boss