I know those conditions. My hairpin turn example fits. Earlier I cited an example of coming up an incline into a 90 degree left turn at a T intersection where the cross traffic has stop signs but I do not. It's dangerous because sometimes cross traffic drivers assume I have a stop sign so I slow way down to watch for a stopped car failing to yield right of way.
The vehicle lugs under these conditions and I wonder if that's what you are calling a "vibration" under lower speed conditions. That lug is the same thing you'd feel in a manual transmission when your RPMs drop too low and the load too high for the gear you're in.
Like I said, I chalk it up to the torque/gearing set up rather than cylinder deactivation. You've got a 187 hp / 4 cylinder / 6 speed in a vehicle weighing 4,600 to 4,800 lbs. It's kind of hard to get flawless shifting under all conditions with that set up. I don't think you'll find a vehicle on the road with that configuration that doesn't give you a lug or a gear hunt under specific circumstances. I cannot account for the folks that sense a vibration at 50 mph because I've never felt that.
Now, if the torque/gearing setup is
because of cylinder deactivation, or
because they've added the manual shifter, or
because they are encouraging vroom-vroom at the get-off, then we're talking chickens vs. eggs, more of a wholistic thing where tweaking one thing affects something else. In another thread about the 2018 somebody attributed this lug to the torque converter, so toss that into the wholistic mix.
I look on the bright side. The quiet and comfortable ride that is well composed over bumps (on the 17" wheels anyway) while having muted body roll in an aggressive turn despite the high center of gravity in a CUV is kind of a minor miracle. I also find the motor gives off a pleasant growl when you put the pedal down. I'll take the occasional lug in exchange.
Cylinder deactivation is for some minor improvement in mpgs, and still the rating is at the low end of the competition with their little turbos and CVTs. I don't think they'll just drop CD without going to a whole different configuration, a small block turbo like the Honda or a CVT like the Toyota, setups that have their own issues.
Mazda entered into a joint venture with Toyota, sharing a plant, for what specifically I have not seen:
HUNTSVILLE, Ala., (Aug. 13, 2020) – Today, Mazda Toyota Manufacturing, (MTM), the new joint-venture between Mazda Motor Corporation and Toyota Motor Corporation, announced an additional $830 million investment to incorporate more cutting-edge manufacturing technologies to its production lines...
pressroom.toyota.com
I joked (kinda) that Mazda will come out with a crossover with a Toyota hybrid drive train. Stiffer fuel economy standards are on the way. It's going to be very hard to build cars if you can't move some significant product with high MPGs, hybrids and/or electrics, to get the fleet above standard.