Then every Forbes list since 1999 is also "false". It's a list accumulating each report from Forbes, as stated in the OP.

Should we fabricate a list just for the Mariah and Janet stans so that their billionaire husbands are included?

well not everybody has the capacity and talent to prosper and advance in life on her own without leeching on others, so since Forbes isn't really a credible source to measure the wealth of celebrities(Madonna herself exposed them), I'm sure they can make another pointless list for them.

And I'm sure Janet has made at least 50m since the list debuted but neither of them are reported enough so

Yes!