If you've been on /economy lately, you'd know that the TPS typically sits around 12-15. A big reason for this is because of water-flushing mob farms. I won't get too in detail on how they cause the lag, but here is a detailed thread by mijiperki [Click here to be directed to miji's post]. This design has literally been proven by studies to lower TPS. I don't see the downside to making this specific design illegal.