Petro,
Well, I stand corrected, then again I've actually never flown out of Moorabbin, so I guess after 40 years I can still learn something new. It was explained to me by someone, either Airservices or DOT/ CASA years ago, that the reason that the runway designation doesn't always match the magnetic heading on 02/20 & 13/31 runways was so that there couldn't be confusion.
Re: 02/20 are there any as I can't recall any at a licensed airport. Then again as I haven't been to every airport or strip in Oz, there's quite likely to be.