Sorry, physicist here, but this is only true in a static environment (which cycling isn‘t): wider tires have more grip, because equivalent pressures (in terms of the size of the contact patch) are lower. At lower pressures, you have more compliance, and it is the increase in compliance that increases grip since you have more and more consistent contact between tire and surface. To put it simply, a narrower tire needs to be run at higher pressures, which means it bounces around more. When it “bounces” the contact patch decreases in size, perhaps to 0 (when it no longer makes contact to the ground). That‘s why in practice wider tires do have more grip.
I would also reckon improved compliance due to lower pressures and the larger deformation at those lower pressures with wider tires is also the main factor when it comes to cornering, not the wider contact patch at rest. Again, you need to look at it dynamically, not statically.