"lesbian" isn't the significant part, "couple" is—while it's not really that significant and can't be classified as an "advantage" in any official way, it does in most cases contribute to attachment and as such in some cases also teamwork.
Okay, but one, it's possible to have attachment to another same-love team member while being heteroloveual, as friendship is a thing.
And two, if being a couple somehow makes them more successful in teamwork, then this only reflects on how poor-quality the other team is. Just because you may be romantically involved with someone doesn't mean you would work better in a team with them.
And then ultimately, there's no mention of this rule being about Lesbian Couples. It's about having multiple Lesbians or other LGBT+ individuals on the same team.
They make the claim that being a Lesbian (or LGBT+) somehow gives you an inherent advantage over a heteroloveual player. Which of course is absurd.
