I would say because Miyahara is a world medalist and has been pretty consistent with the short program this season - was first at 4CC, for example. I think the free skate with more jumping passes which could be called under rotated will cause her more problems, plus the title of this thread says all skate clean so that means to me that she hasn't under rotated anything.
Even if she has no URs though someone like Daleman will get much more GOE. Miyahara might get higher PCS than someone like Daleman but she doesnt get Medvedeva or Kostner PCS from the judges either, not even close. Arguably she should but she doesnt, and she didnt even in 2016-2017 when her stock was the highest and her PCS arguably should have been as high or higher than someone like Medvedeva. Someone like Daleman if she skates like Canadian would likely beat her from the GOE on the jumps IMO. Anyway as a reigning world medalist and with the buzz in the skating community from her thrashing of Osmond at Canadians I am sure she has atleast as much respect from the judges as Miyahara does currently, probably more in fact. I dont see the judges giving Miyahara a big PCS edge on Daleman which IMO is the only way she beats her in this scenario, as Daleman would clearly come out on top in TES.
Someone like Chen would have a very good shot to beat Miyahara out of the final flight if both are clean with no UR calls and she wasnt even on the poll. I think having Tennell on the poll and not Chen is ridiculous, Tennell is more likely to skate clean but Chen skating cleanly with no UR calls would easily beat Tennell, I am almost sure of that.
Nagasu with a clean triple axel probably beats Miyahara too, just because of the triple axel.
Really everyone on this poll would have a decent shot too, not sure for everyone but a decent shot, minus Tennell who definitely loses to Miyahara clean to clean, and maybe Sakamoto just due to being Japanese #2 even though many aspects, like her technical elements beside many of the spins, are better than Miyahara. I think in the unlikely fantasy everyone is totally clean Miyahara is likely out of the final flight, even with no URs. Especialy now with Nagasu doing a triple axel which means in the hypothetical clean she probably beats Miyahara whereas otherwise she would not have.
And it is a no brainer Medvedeva, Zagitova, Osmond, and Kostner (now that she has upgraded her combo and seeing how her SP was scored at Europeans) would easily beat even a clean Miyahara if they are also clean in the short. And the likelihood atleast 2 others would is quite good.