There's no difference whatsoever in the cache regeneration time, and nothing that can be attributed to the 2.3 update.
I tried it now, and forced a complete cache regeneration ( by removing the %PROGRAMDATA%\Virtuali\Couatl folder ) and the cache regenerates entirely in 2 seconds, with the default P3D sceneries set. Of course, if you have many add-on sceneries, it will take more time, but that's a complete regeneration, that is not supposed to be happening if you just add or remove a single area.