maybe because every LLM provider has an "attach file" feature so you can attach a paper and then ask questions about it?

what's the value add of the wrapper that this person wrote at all?

I built it because it was tiresome to save the pdf, open a new window, add it and give a prompt.

Simply replacing the domain arxiv.org with asxiv.org does all that for me now.

Also it links to pages in it's answers and scrolls the pdf to it on click, allowing to view the pdf side by side with the chat.

Right. I do this all the time with Gemini. Add a pdf or a link and ask it whatever I want. It will even turn it into a podcast with two people discussing the entire paper that I can listen to on the tram to work.