Is flap necrosis likely to occur now or would it have showed some sign that it wasn't taking before the 3wk period? (photos)

Nearly 4wks ago I had mohs surgery to remove basal cell carcinoma from my nose, it left quite a big defect and my surgeon opted for a washio retroauricular flap for reconstruction. I am due to have it divided on Monday but my surgeon wants to clamp it first to see if it will survive, how likely is it to develop flap necrosis at this stage, would it have showed any signs before now that it wasn't going to take?

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