[f5fstop]

First, let's understand there is a difference between, all-wheel drive, part-time four-wheel drive, full-time four wheel drive.
In an all-wheel drive system, a small percentage, usually around 10-15 percent is directed to the non-drive wheels. If there is slippage detected, up to 50 percent can be directed to the non-drive wheels. This can be done mechanically or electronically, and the actual percentages can be different depending upon the manufacturer.
The H3 does not have what is known as a all-wheel drive system. It has a full-time four wheel drive. In non-lock, there is 40 percent power to the front, 60 percent to the rear.
Lock the case, and it will go to 50/50.

(We should all know the difference between full-time and part-time four wheel drive.)

As for the initial concern, if GM programmed it to unlock at 45 and someone needed it at 50 (for example), they would be upset.
Hate to sound sarcastic, but that is what the lights are on the dash board for; to signify if you are in open or locked 4-wheel drive operation.
I guess they also expect those who engage 4-wheel lock, know that they have to turn it off.
As for damage, I would bet you did no damage to the case.