Has anyone ever experienced ... or am I going crazy?

Has anyone ever experience a P0420 code that was caused by a malfunction in an engines variable valve lift system?

I've seen it ... just checking if anyone else has experienced this situation.

I have not seen this specifically related to VVT exactly, but it is not uncommon for a cat efficiency code to set alongside a problem that effects the air fuel ratio, like with a misfire, rich condition etc. Fix the mixture and fix the cat code.

BMW/MINI VVT is called valvetronic. I was chasing a P0420 code for a while. What really threw me for a loop was when I performed an O2 storage test and it passed. Downstream O2 sensor running at about 720 mV. I cleared the codes, but the P0420 returned. So I performed another O2 storage test; it failed the 2d time. I installed a new Cat under warranty; and cleared the code. The P0420 returned 688 miles later. I cleared the code. Shortly thereafter, I got a DTC for the valvetronic servomotor. After checking power and ground, I replaced the motor. Now I've got 2200 miles on the car, and no DTCs have returned ... same Cat, same downstream O2 sensor. The only thing I can think of was that a problem with the variable valve lift servo motor was intermittently allowing too much or too little air to enter the intake. It's weird for sure because every time I checked the fuel trims they were perfect.

That's a new one for me. 

I have seen a dirty MAF cause a false P0420 on a Toyota. Super lean trims, loss of power. No lean or miss codes, but it'd happily set a cat code. Never really figured out how the ECM screwed that call up so badly...