It really doesn't make a difference. You can use a mobile subscription for only data and you will still need a [S]ubscriber [I]dentification [M]odule to make sure the subscriber has actually paid. And even if you didn't have a SIM card, or swapped in a new one every 5 minutes, your physical SIM card slot would have the same IMEI being shared with the mobile provider.

Though this information is all pretty much useless by itself. If you use HTTPS then your mobile provider can't see anything you do on the websites you visit. If you use a VPN then they can't see the websites you visit at all. All you are to them is a dot on a map. They won't even have your name if you don't explicitly give it to them when buying a phone and mobile plan from them.