Due to the lack of saturation in the moderate event container, solargrubs show up way too frequently, and changing the frequency doesn't help. The container has to pick. This change will just bump the drain speed down so severely, that if you kill one or two grubs, the station should barely feel the impact anymore. As opposed to having to kill 4/5 grubs on average.
Gradual nerfs seem logical, as grubs get more and mroe of a day-to-day experience, and most people know about them now. Time to stop the witch hunting for those annoying grubs :p