Well, there is no any info that Quokka and Wombat are somehow "connected", except they indeed look quite similar. For Wombat, in various dealers' coin description it is said that it's the start of new series, although I couldn't find such wording on Perth Mint site. Maybe it was said in internal communication from Mint to the dealers.
As an example, here is the LPM page:
As to the coin itself, I can't say it's the best example, the usual Perth high quality, but quite dull design. In fact, I like Quokka much m