Sounds likely, I haven’t used port forwarding with my VPN since Mullvad stopped supporting it, so when I recently shared my own torrent I paid for 1 month of a seedbox just to make sure it seeds well and the seedbox uploaded ~50GB while my local setup on a VPN without port forwarding only uploaded 1.8GB (and it hardly showed any peers as if nobody was trying to download). So it seems peers had a much easier time connecting to the seedbox.
I have since setup port forwarding in gluetun for my local torrent client. I just wish there was more support for it because gluetun only has built in support for port forwarding for 2 providers (I guess automated requesting a forwarded port), and even then you still have to make your own script to automatically set the port in the torrent client when it’s assigned / changed. It’s possible that some providers do it more like Mullvad where you get assigned a port via the website that is tied to the VPN credentials, so you just have to plug the assigned port into the torrent client settings (that’s how it worked with Mullvad so I could just enter the port once and forget about it) but I haven’t checked other providers to see.
It was waitlist for a while, not sure if it still is but I got my welcome email like a week later.