penalty turns

The primary job of a protest committee is to fairly establish whether any rules were broken. Any penalties that might or might not have been taken subsequently are irrelevant to that.
Only once they establish what rules were or were not broken does whether penalties were taken become important. An obvious possibility, for example, in a close situation, is that the PC finds that both boats broke rules and neither are exonerated. In that case the boat that took a penalty at the time would most likely face no further penalty, but the other one would be penalised, normally DSQ.