Sicne all wheels are traveling at the same rate of speed, when you take a turn, the front wheel(s will want to turn faster. This isn't good for the AWD system. Sure the wheels will slip a bit but it's still not good.
Even worst in a true 4X system such as my 88 Ford Ranger. Okay going straight or in lose sand/gravel roads.
It's always 2-WD in my opinion. i.e. only 2 wheels can have traction on a AWD system without lockers. Read if say the passengers side wheels are on ice, they will spin. The drivers wheels are on dry pavement you will go nowhere. Even my Jeep GC (pre 96) AWD would get stuck this way.
Power will still go between the front and the back with the lock turned off but the system will adjust the amount.
With the lock on it will be 50/50.
There has been a lot of discussion about this on this forum as well as others that really get into the system.
This is just a brief re-cap from my understandings.