New Hotfix Arbitration defense

[MarketShark]

Hello! Actually i have tried 3 different Defense. 2 grineers and  1 infested i think . The wawes from 1 to 20 are really shorter, like  20 minutes around. But i've notice that the wawes fomr  21 to 30 are far more longer than normal, like the same before the hotfix. This can be notice expecially vs Infested. The infested just keep spawning wnon stop for 2-3 minutes per wawe almost. Is this intended? Like first 20 wawes shorter and the other much longer? I don't know if this is a bug or intended like i said. Thank you and sorry bad english.