On Windows PowerShell Core use file extentions from PATHEXT env variable to run the file as executable.
On Unix we ignore PATHEXT but it can be useful. (See #7697.)

From #7697 (comment)

@PowerShell/powershell-committeeTeam members are private reviewed this and it seems that $env:PATHEXT can provide utility on Unix systems if the user creates the environment variable. Example is if user has foo.py and wants PowerShell to execute foo, they can use this.