The problem is that during such air-naval blockade, the PLA warships implementing such blockades would be extremely vulnerable to adversaries' surprise attacks, not mention the blockades would give the QUAD sufficient time to mobilise. The end result would still be a war of attrition.
The air-naval blockade also means air support for vessels during the blockade, including creating an NFZ around the blockade of Taiwan, regardless of its magnitude. If an enemy vessel is approaching, will it be a warning target or a real target that can be attacked, if there is a need for such an act, furthermore, considering China's ISR capabilities, I highly doubt these surprise attacks, unless they are the underwater threats.
We are in a dilemma.
China will not be able to hide the pre-preparation of the attempted landing in Taiwan, as soon as this movement and concentration in China were taking place, do you really think that the QUAD will stay put, waiting for China to attack, if it really is the will of all of them go to war against China to defend Taiwan? They will also be preparing and mobilizing, which further shortens the time lag for China to conquer Taiwan, so I would highly doubt this week-long lag before the QUAD mobilizes.
As I said, we have two situations in which the QUAD will hypothetically intervene.
China carrying out all the pre-preparation for the amphibious assault and mobilization of ground units, denouncing its real intentions, this can be put in months or weeks of anticipation of recognition by the QUAD, I don't think that all the QUAD countries will stand by while China is preparing to invade Taiwan, if the intention is really to go to war against China over Taiwan.
Or
China carries out the entire air-naval blockade on Taiwan for weeks or months before landing, wearing down the entire ROCA, simultaneously waiting for the full american and allied response, which ensures the PLA manages the escalation, recognizing whether Taiwan's allies will intervene or not .
In any case, in both scenarios, the PLA would be in a war of attrition, the difference is that in the first scenario, ground units would have already been deployed to invade Taiwan and in the second scenario they would not, the contingency up to this point in this last scenario it would essentially be air-naval.