By cutting, they're centralizing authority at the top. More and different rules will come - some written, many not - but not by the people that were in place before the change.

Not really. Authoritarianism is more about centralization of power and getting rid of layers that could interfere with the central authority's ability to project power.

Lots of rules tend to constrain an authoritarian ruler's ability to act at whim.

No, bureaucratic authoritarianism (our current system) does not encompass all authoritarianism. The flavor that has just been set into motion is autocratic authoritarianism, which is actually closer to what most people mean when they just say "authoritarianism" (hence this gutting of bureaucratic that would otherwise slow it down). That perspectives have been able to become so warped as to blissfully ignore the horrors of autocratic authoritarianism really just shows how out of touch voters have become.