It is. Mostly. You are downloading them from wherever it is you are getting the video, then you are using a client to upload them to whatever hosting service they default to. Looking at your history, it has been nostr.built that they are defaulting to.

If you don't have a paid account with them, there are file size limits, though. They recently increased the max file size for users of their free service to 21MB, but I am unsure whether they have a daily/weekly/monthly limit as well. The site doesn't say.