AOM:
I have a sheilos rav and I looked through the whole sefer for this question but I didn’t find it. Is it in a different sefer? At least I can say for now ein danin min hamaiseh.
Either way I don’t think he meant mamush assur. The Torah only assured using a razor.
That being said I’m a strong proponent of growing beards and have one myself. My previous Rosh Yeshivah says a beard and peyos is part of the tzuras haYid. And the mekubalim are also very makpid on it.
EDIT: Also the chazon Ish writes in Igeres 197 and 198 that the derech haYashar is to at least leave short hairs that can be termed “a grown beard”.