"Jesus has just defined marriage as a male man to a female woman, and that's how the men to whom He was speaking understood it."Your conclusion is not at all what Jesus actually said.
The Jewish men to whom Jesus spoke did not define marriage as one man with one woman for life.
It also leaves open the strong probability that God intended the 5% of humans who are same sex attracted to be same sex partnered.
Your opinion differs from what the texts actually say.
The Pharisees did not ask Jesus if "same sex sexual relations are always outside the marriage covenant." Your interpretation substitutes your opinion - something Jesus didn't say - for what Jesus actually said.
"That's always been the orthodox Jewish position..." Your statement is factually inaccurate.
Jews throughout the Old Testament and into the first century AD accepted and permitted polygamy.
This provision is never described by Jesus or any human author of scripture as accommodating human sinfulness, yet Jesus did describe divorce as sinful, Matt , 19:3-7, Mark -12.