I don't get it. If your school has a deadline for withdrawing and you withdraw after the deadline, there isn't any consequence?
While the AMCAS WF policy isn't explicitly stated on the website, they do refer to incompletes:
"A course is considered Incomplete if the work required for it was not
completed within the appropriate time limit. If the Incomplete is
unresolved, no AMCAS grade will be assigned; however, if the Incomplete
is resolved, an AMCAS grade will be assigned. Select Incomplete even if:
o A grade has been ultimately assigned, or
o There is no notation indicating Incomplete on the official
transcript.
Many schools will assign an "IF" or "F" grade if the coursework is not
completed within a given time limit. If attempted credit hours are listed on
the official transcript or can be determined by AMCAS, this "F" will be
included in your AMCAS GPAs."
I'm not exactly sure about your case of withdrawing, since your school seems to treat withdrawals the same before and after the deadline. Looking at the AMCAS Policy, it might count as an F, even if your institution doesn't count it as an F.
You should probably contact AMCAS anonymously and ask them.