The author of that tweet clearly has an issue with the arxiv being an open repository where everyone can upload anything. There is nothing about open access in the tweet. And arxiv is not same as the concept or movement of open access. Most articles on Arxiv doesn't even have a proper license to fulfill the definition of Open Access in the BOAI declaration.
Further proof that the authors tweet is not about or against open access is that she publishes open access herself:
Further proof that the authors tweet is not about or against open access is that she publishes open access herself:
https://jlm.ipipan.waw.pl/index.php/JLM/article/view/292
https://nejlt.ep.liu.se/article/view/4017
https://dl.acm.org/doi/10.1145/3498366.3505816