I hear the argument, but I wonder if you think judge would see that distinction as a valid argument in a court. A big part of the legal system is to actually see similar thing as being similar, even if there are technical differences.
Technically you can not track a person online. You can track an IP address, or a cookie, or an ID string in a database, but the server does not have eyes on the person behind the screen. Anyone can be behind the same IP address, people share accounts, browsers and devices. A operator can never be 100% sure if a data point identify you or anything about you.
But I don't think a judge would see that technical distinction. European courts already see mobile device location data as private data. So I ask you. What do you think a judge say about location data on peoples cars. Personal data just like mobile phones, or not?