Bloody annoying when Physios only pay attention to the symptoms - you end up where you are.
Stretching is never the answer, just a cute little pain reliever. Just as piriformis syndrome is never the answer - it's just a collection of symptoms.
Sounds as if your 2nd Physio took a step forward - tight upper back and then took a huge step backwards - stretching hip/piriformis.
Go for the cause (poor posture, tight upper back, poor glut control) not the symptoms (hammy, glut, piriformis)
You haven't got the ability (yet) to move better when running, so you end up with a functional (how you run) issue. Try this thoracic spine stretch https://www.sixphysio.com/video for the next 10 days or so and improve your sitting/work/running posture - there will no over night miracle cures, but give it a blast....