I guess it depends on what level of risk you are comfortable with... but considering that people have literally gotten notices when NOT doing anything illegal, like this one:

https://torrentfreak.com/comcast-subscriber-receives-dmca-notice-for-downloading-ubuntu-210526/

My reasoning is that it is better to just hide everything you do from your ISP bc even if you can get the court case dismissed / the warning ends up just being a threat with no teeth, VPN's aren't that expensive and I don't want to have to waste my time dealing with greed corps at all.

But you do you