[ersiees]

Another clue: there is no way to download the latex, while you can if someone uploaded the latex on arxiv.

[cauliflower2718]

There's a lazy way to submit to arxiv, which is to submit just the PDF, even if you did it in latex. Sometimes it can be annoying to organize the tex files to submit to arxiv. It's uncommon, but the font and math rendering are the standard latex font.