The reverse can be said as well, that PRC isn't buying the idea that US enforcement of freedom of navigation is unrelated to its military surveillance of strategically important military facilities.
Let's put out a hypothetical question here -- do we think China would be pressing its claims or seeking to enforce them in such a great urgency if there was not such consistent US surveillance aircraft and ships near China's important facilities?
Let me pre empt a response, by first saying that yes, China has also on occasion sailed and flown similar surveillance flights, and it is within the rights of the US to use whatever legal means to achieve its aims -- even if this includes forward positioning and conducting intensive and comprehensive reconnaissance of a potential foe's strategic military facilities such as nuclear submarine bases.
However China also has the right to use means to try and pre empt it in whatever means within the flexible bounds of international law.
What I do not find reasonable however, is when one side tries to use freedom of navigation as a lead in for conducting these kind of surveillance actions. If the US straight up said "we desire to have overwhemling ISR for our forward based air and naval assets against our strategic competitors" -- that I can accept. I don't even need the US govt to acknowledge it, but it would be nice if we on an online forum that talks candidly about military matters can straight up describe each other's intentions.