Facebook/Meta has been doing open research in ML and NLP for far longer than the current LLM era: Convolutional Neural Networks for Sentence Classification (2014), FastText (2016), PyTorch (2016), fairseq (2017), LASER (2018), RoBERTa (2019), XLM-R (2019), and BART (2019),

They were always present at ACL with decent open research as far as I have been studying/working in NLP (2014).

It's part of a strategy to attract top talent in the field. If you want top researchers you have to let them publish, which in turn hones a reputation of solid research, attracting more talent.