Why isn’t the third party software ban enforced?

[Halivel]

Sadly far from realistic, a boss don't stand still and mechanics happen.

True, but dummy is still a more or less accurate way to check your perfomance. If person can't beat a dummy despite it standing and not having mechanics - they're clearly not good enough to clear the content itself. If they're beating on last 5 seconds - they will struggle. If there's decent leftover of time - they're okay.