But gliderecord script does not check acls, right?

The gliderecord stops working/ or does not return result set when called directly from client side in a session where the user does not have sufficient privilege on the queried table.

I am seeking some documentation/ actual reasoning on this.

I agree to this...
It has to be an ALC issue...
Cant verify this now but that's what comes closes to hand. 

The Non admin user might not be a member of assignment group

no, not the case.
You may try the example in personal instance.

Hi 

Check the BR i.e user query which defines the sys_user(User table) only for admin(till kingston version) and for admin,user_admin(From London). Check that query BR.