I am Hideaki Hagiwara in Japan.
I think same problem IDEMPIERE-2347.
I found that MMatchInv class have reverse() method and use IsPosted() like a MMatchPO.reverse() method
And MatchInvReverse and MatchPOReverse that are process classes use isPosted() to check before perform reverse() method.
But I consider that this problem is not typo bug.
Order of posting is important for some Cost Accounting method.
I made patch.
Please check it.