I suspect China doesn't want to deal with a Republican Congress...they might move before our guys take office. Or worse, they'll make the invasion the 'October Surprise' as a gift to Biden. (I suspect the Chinese are happy Biden's in office and his whore monger, drug addicted son is still in tight with Daddy)
An invasion the size necessary for even a small Taiwan will create a foot print of preparation nearly impossible to miss. If China is going to get froggy it will either take some of the Taiwan administered islands nearer the coast or if they are really bold initiate a blockade