I was reading elsewhere ("Τα παιδιά έχουν ένα φυσιολογικό κεφάλι") that often in Greek the singular can be used in a general sense, where a plural would be used in English. In this sentence multiple peaks would in practice imply multiple mountains, so doesn't the same apply, in other words "the peaks of the mountains"? Or is the sense here definitively singular?
Yes, there are other mountains named "Olympus" in Greek and other nations...even on on Mars.
The one we all know from history is in Thessaly.