It just removes the OnBeforeRequest() way of injecting javascript. There are other directly supported ways to inject javascript, some of them easier than OnBeforeRequest(). The counterpoint would have to be something like removing that was just the first step, and that they plan on closing all the doors. But, if you close all the doors, really all the most popular extensions are hobbled.

Edit: Removing just OnBeforeRequest() js injection does sort of uniquely harm mostly heuristic ad blocking and things like tampermonkey. It's not hard to feel like that was probably the real goal.