I did.
And if the result of having someone proofread and give “suggestions” is that the prof thinks the students couldn’t possibly have written it, those suggestions were probably substantial enough that they should have at least checked beforehand. If nothing else, it won’t come as a huge surprise to the prof.
Also, if their response had been “we took it to the learning center and one of the tutors there helped proofread it and gave some suggestions on how we could improve it,” I have a feeling they wouldn’t have had nearly as much trouble, since the learning center (a) has record that they were there, so we know they really wrote the paper and (b) has tutors who know how much they’re supposed to help and how much they’re supposed to require the students to do on their own.