I would not say "bad" directly. Just not good.
Sometimes there is a need to rig up some temporary arrangement for testing purposes or as a interim fix for some problem.
With respect to fans and cases a properly designed and implemented cooling system should
not require you to duct tape in an extra fan.
And the temporary fix may appear to help but the airflows may be insufficient in some matter and overheating could occur over the long term. Or there could be other side-effects that impact other components/cooling.
Not at all usual for "temporary fixes" to work and work well for long enough become permanent.
There are always trade-offs with such things.
Just my thoughts on the matter and others may comment as they feel appropriate.