Yes, in 2017 Cherry changed the design of their switches. The design change, whether by accident or design, corresponded with a significant improvement in smoothness. “Retooling” just means they got new tooling, i.e. new molds.
As for what changed, the sliders are visibly different. See here for details. The housing and/or contact leaf also might have changed, but I don’t think anyone knows for sure.
All Cherry MX switches except Clears are using the new “retooled” molds. The “retooled” qualifier distinguishes modern Cherry switches from their counterparts in the 2000s and early 2010s, which are inferior. Anything sold by Novelkeys or KBDFans will be the “retooled” variety.
As Nebulant mentioned, Cherry switches do appear to ebb and flow in quality. It has been reported that smoothness has been declining over the course of 2018; I have corroborated this report, but only with a sample of 10 switches. It’s possible that the injection molds wear out over time, leading to a rougher surface finish. If you buy them from an electronics supplier like Arrow.com, you might receive a factory “date code” on your package. However it’s generally not possible to know which “batch” your switches came from unless the vendor tells you the date code before you buy, and I’m not aware of any vendor who does that.