Rowena is a cut-throat ruthless businesswoman who reportedly fully intends to take a seat on Ul'dah's Syndicate, and sees little difference between goods and people when it comes to making more money.

Mowen is a newcomer to the business of dealing in tomestones, and expressly intends to give back what profits she has to improve the lives of everyone, both around her and beyond.

They are literally the opposite in personality.
I'm not really sure how you reached that conclusion? Mowen also pays all those in her employ with monopoly money that can only be spent with her own business, while skimming off the top of every sale. She's exactly like Rowena, who similarly likes to give her enterprise good PR with things like "The Center for Cultural Promotion".

If not for the fact that we had an interview expressly warning us not to assume that "meeting similar people" does not equal "these people have shared souls", I might have even been agreeing with you.
All they said was that characters being similar does not "necessarily" mean they have the same souls. That doesn't mean similarities aren't evidence towards sharing souls. I'll also note that developer statements haven't exactly always been the most reliable things in the world. "Ending the Garlean Empire Once and For All" in the fanfest prior to Shadowbringers springs to mind here, or Yoshi's statements about FC and private housing totally being different, and more besides. Basically it was just to give them some flexibility and not have to directly address the issue.