Good morning @tiateacake may I ask if you are asking -" IS or ISN't a flare up "?? if my memory is correct I think in this webinar Sebastian Sattui makes point that a flare up will have the distinction of the reoccurrence of Stiffness - not pain. {and what I recall as being very weird feeling in the morning}
https://connect.mayoclinic.org/discussion/comprehensive-overview-of-pmr/.
When I was tapering I was very keen about noting any symmetrical pains - for example I was writing down that I had pain in the shoulders down to wrists . I had an open 'script to get CRP levels checked whenever I felt was necessary. I also happened to have an appointment with my osteopath and she manipulated my neck , and voila' , those pains were gone.
As many others have related , the tapering below 5 mg is tricky ! Can you just go to the pool and float and relax ? ; )