Why not? Remember the appeal is about the claim construction - intepretation of claim terms, not the final decision of patent validity/infringement (if parties went to trial, juries would decide the later).
I Don't believe ARM's PR that they are clean and their customers are safe from now on. ARM was kind of self admitting that they are still hooked by 749 by submitting reexam request to PTO recently. Let's wait for TPL's response.