It is two women, he perceives them both as women, and he has lust.

If the monk, referring to the anus or the vagina of both women, praises, disparages … or abuses, he commits two offenses entailing suspension. … (To be expanded as in <a href='https://suttacentral.net/pli-tv-bu-vb-ss2#3.2.4'>Bu Ss 2:3.2.4</a>–3.2.36, with appropriate substitutions.) …

Referring to the private parts of two beings of different kinds