My thoughts exactly.
The whole reason a stay was granted, is because SCOTUS could reverse PA Supreme Court’s ruling. If PSP starts acting on that ruling now and SCOTUS reverses it later, imagine the chaos that would create.
Also,because there ia a stay, the law is still exactly the same. Nothing has changed. There are no grounds to file a writ to force PSP to comply with a change that hasn’t happened yet.
An attorney might gladly take the money and file the writ, but it won’t go anywhere, at least not until after SCOTUS denies or decides this case, but by then, it might not even be necessary.
*** I am not an attorney. Nothing I say should be taken as legal advice. I could very well be wrong in my speculations ***