Maybe, but there's not much value in fighting over definitions. De facto, they have not annexed anything.

This is nonsense. You're attempting to redefine what annexation is to suit your argument.

Oh, are countries not allowed to sail ships through international waters now? Is the US annexing these territories when it does the same thing?

China themselves claim that their boats are patrolling their own territorial waters when sailing in these areas. The US and Canada and others claim they are sailing in international waters under international maritime law, or with the permission of the nations whose water they are sailing through.

But the big difference is that the US isn't making a claim to any territory. China is, and then they're attempting to assert that claim with their navy. That is clearly annexation.