Some brand new BMX dirt bikes come from the factory with a larger tire in front. This is for better handling or traction on the dirt. In a panic situation, or a low traction situation you want the back to break loose first. So you put the bigger tire in the front. In dirt bike motorcycle racing where you routinely slide the bike on the dirt you want the back tire to go out first. That way you can control the slide better. This is going on every day. I did it for 25 years at least.

Putting a larger tire on the back to handle the load better is going to make your bike handle poorly even unsafely in a panic stop. You have more rubber on the road in the rear. You may possibly slide the front tire first when you don't want too. It's much harder to keep upright if the front tire starts to slide.
The bike manufacturer knows this. They sent the bike out with two of the same size tires, and they know how that bike handles in a slide. They ship the bmx bikes with a safe tire set up from the factory, just like all the rest of the bikes with the same size on the front and the back. They understand.

I am now climbing into my Nomex Flame suit and a fire proof hole in the ground. Let me get a drink of water before you turn on the flame throwers.