Simply stated, True ownership of a condo, villa, apt. etc. normally does include a MF paid at agreed upon (monthly/quarterly/annual) intervals.
Timeshare is not really ownership of property but an ownership of an agreed upon week or weeks at a resort and MF for same is normally billed annually. I do not know for certain but would assume the folks at our timeshare facility that have timeshares of 3-4 months understandably negotiated a reduced rate for their MFs.