You’re attempting to redefine what annexation is to suit your argument.

Fair enough, I did not phrase the above point correctly. I have edited the comment accordingly.

That is clearly annexation.

Since you keep using this word, I guess I'll bite a bit longer in fighting over definitions...

Courtesy of Merriam-Webster, annexation is incorporating "(an additional geographic area) within the domain of a country, state, etc." I don't think it's self-evident that just sailing a ship by some islands is "clearly annexation"

In any case, it's not really important whether it counts as "annexation" or not. What difference does it make if China makes this claim if there's nobody there to enforce it?