I guess it depends a bit which field they work in exactly. I'd be rather surprised if rigorous DL researchers in NLP haven't heard of him because I expect "Universal language model fine-tuning for text classification" (and tbh. also "Fine-tuned language models for text classification" due to the universality of the idea) to show up in any half-decent literature review of the field.

Most DL researchers I know also have a pretty good knowledge of available libraries and make it a habit to check them pretty often.