Yes, the first thing many drivers generally think about with new tyres is that they want more tread on the front for better steering and better water clearance in order to avoid aqua-planning. What some people fail to consider is the impact of all that additional grip at the front on how the back tyres behave. The theory behind the Michelin poster probably comes from the understanding that it's easier to control under-steer that it is over-steer, and that more tread on the back helps resist this. Having had a lively (but fantastic) BMW 320 in the past, I know that over-steer was easy to induce in the wet regardless of how much grip you had at either end
. With experience you can manage it to a degree and it feels intuitive. It's under-steer, when you're drifting across the road into the path of a lorry, that backing off the accelerator, avoiding the brakes, and having the front end regain grip feels counter-intuitive.
On the subject of the 1.6mm limit, this was also discussed on a previous thread. It was determined some years ago based on how much tread depth would be needed in order to disperse a certain amount of water, at a certain speed, and with a certain width of tyre. From what I recall, it was based on a tyre width of around 185. Tyres widths on many cars, including the Ateca, are now much wider than that so logic would suggest more tread depth required to achieve the same result. That's why you might see suggestions at some garages to change tyres at 3mm even though the law says 1.6mm.
Michelin are now making car and bike tyres which they say are just as effective at 1.6mm as they were when new. At least they've recognised the need for change even if the law hasn't.