First thank you for taking a look and holding my feet to the fire.
Have several packages based on strictyaml. What matters is YAML files are validated against a schema. Whether use .yml or .yaml is personal preference. My personal preference is typing less characters. Both should be allowed.
Share your hatred of Windows and don't even see it as a serious OS. So was actually surprised that .yml has some association with Windows or MSFT.
If while using any of below packages, you find the .yaml suffix is not recognized, that would be a bug. In which case, create an issue.
These published packages could be affected:
To actually confirm has bug status, would have to review the unit tests and see if .yaml is not tested nor recognized. Otherwise it's mere conjecture. It's an unconfirmed possibility. Maybe you are right, maybe not. Or maybe you are on to something.