Earlier quoted context omitted.
You are not obliged in any way to use the service. It is purely optional. If you choose to use it, you consent to some things.
Sorry, but you don’t seem to grasp the concept of “opt-in”. The service is optional. The tracking is not opt-in, given you choose to use the service.
Some might say "Thing B is optional", because thing B is attached to thing A that is optional, and their inseparability does not change this characteristic.
I understand where you're coming from. It would be really awesome have privacy-respecting to have an "opt out of all tracking forever and just let me have the service" button, without which there's really no option at all. That's a strong, principled, justified, and completely valid position.
Yet, it's perhaps possible that different vernacular readings of the word might arrive at different, though equally valid, positions.