I emailed Bruce Carter directly and he responded promptly. I don’t think withdrawing an application when you have more enticing offers would ever be taken the wrong way. What schools/PIs disagree with (my SO and friends are all in grad school so I’ve been privy to the details of a lot of application cycles at various schools) is handing out an offer to someone who has either accepted elsewhere or who is not still considering their program. I think your paranoia is unfounded. If you wait to the last second (eg if you receive an offer on say the 15th) even rejecting at that point might preclude them from making an offer to someone else or it might force a willing applicant waiting to hear back to accept elsewhere prematurely. There is absolutely no reason to hold on to an application for a school you don’t wish to attend.