The whole "threat model" thinking is useful for security, but I don't think it translates well to privacy and data sharing consent matters.
Regarding the privacy:
If you are using a VPN to protect your privacy, then you are effectively transferring your trust from your ISP to your VPN provider. The VPN provider is your new ISP. So you have to make sure you trust the VPN provider more than your ISP.
In my town there are 2 ISP I can choose to trust, whereas with VPN I can choose to trust from a much greater selection.