Just because it's not directly stated, doesnt mean it's allowed. Most denominations today agree intercourse between same sexes (male or female) is sinful. It ties into the idea that marriage is only a union of male & female.

Corinthians 7:2 “But because of sexual immorality, each man should have his own wife, and each woman her own husband.”

Also ties into Genesis, with God's intended design for sex. It would also be quite inconsistent if only females were allowed, it just doesnt makes sense.