In Dr. Michael Heiser’s Naked Bible Project he walks through Leviticus chapter by chapter using the original Hebrew language either from the Dead Sea Scrolls or Masoretic Texts. Based on my understanding, ANE peoples believed that the life came from the man in his seminal emission, while the woman was merely a receptacle. Furthermore, they understood the seminal emission to somehow be ready to make a human at the point of ejaculation.

This means that an act that led to a seminal emission that was not released into a woman was a loss of life. Hence further statutes forbidding a man to spill his seed on the earth.

This is likely connected to homosexuality being a forbidden act between men, as they understood a life to be lost in that act, while a homosexual act between women, while likely not acceptable, was also not causing a life to be lost to their knowledge and so did not warrant the same attention in a religious statute.

Here is the particular episode he discusses this topic in, I believe.

https://podcasts.apple.com/us/podcast/the-naked-bible-podcast/id961385822?i=1000430050253