Grove in brake shoes

My rear brakes are locking up after I just put in new wheel cylinders and new canadian non genuine brake shoes. I suspect that the shoe material is to gripy. I have just bought some second hand genuine shoes from a wrecker off a diff that has never been on a vehicle (factory leftovers). These new shoes have a grove about 1/2 " wide in the centre obviously put there by the factory. I have never seen this before. Are these ok to put on my 95 XJ and what is this grove there for.

The groove runs down the length of the friction material, correct?

If so, that's for dust and water accumulation to find a way to "run off" the friction surface. It will NOT lessen the braking capacity, but it WILL reduce the possibility of brake squeak.