I don't know,if it is so a cultural thing, there has been a nice and passionate debate where different members from differet cultures expresed their expirences.
I guess it is more about where you draw the line, for yourself and how open minded you are.
I was raised Bi Cultural (Romanic - Germanic) and I had aquiteances who did this, from both cultures, without being lesbian, (most extreme example is the Daughter of an German Ex couple who now grown up and having a chiled is in a happy relationship with her former bestie, although both girls Autodefine themself as BI or Pansexual, you name it

Im not specially turned on by Lesbian content the same that im not exited by Voyeristic content, (although, watching porn, Playing this kind of games is to somepoint Voyeristic, again not saying it is good or bad, is more about how you feel about.
So I am pretty neutral about and when it comes to a threesome, i enjoy seeing the girls having Interaction between them, as well that the light Femdom or Dom, It feels for me more like Roleplaying, than BDSM but then again, My own personal definitons and my confortzone may differ form, others.