No, I'm saying /21000/ will match a path with a directory named /21000 but not a file named /21000.
When I say "non-standard", I am saying am saying that if the website's URLs looked like "/21000/foo" and "/21000/foo?page=2", it would have been easier to craft a "Disallow" rule that would have successfully blocked all of the desired pages.
When I say "non-standard", I am saying am saying that if the website's URLs looked like "/21000/foo" and "/21000/foo?page=2", it would have been easier to craft a "Disallow" rule that would have successfully blocked all of the desired pages.