It's definitely the car switching from regenerative 'braking' to actual friction pad brakes because regen can only slow the car to about 2-3 mph. Perhaps the software version in your 2014 is better than your 2016, or perhaps there was an update to the software that you're missing from the dealer?
I don't feel mine 'clunk' on my 2015 but I absolutely can tell when it shifts from regen to friction pads.
Mine feels different depending on the scenario, for instance if I was using regen only alllllll the way up to the last couple feet and barely rolling along the transition is pretty smooth. If I'm braking with medium force I feel the transition more abruptly. If I'm braking hard I feel the car using the friction brakes PLUS regen and the transition is completely unnoticeable because both brakes are engaged.
Sometimes, at low speeds as I'm using the brake pedal lightly and get down to single digit speeds, the car STILL lurches forward as I press the brake harder and harder until I have to slam on it for it to engage the friction brakes (b/c regen can't get you down to 0 mph) and then it's violent and my wife gives me a side glance and I say, "It's the stupid car's blended brake system, sorry!"
I wish they would have let the regen be attached to the accelerator pedal and friction brakes to the brake pedal only. That way I could use either one discriminately rather than the system choosing for me and often choosing wrong or harshly.