The glowing effect allows you to see entities effected with it through walls and blocks. However, this doesn't apply to mobs. They will not see you through blocks if YOU are affected with glowing.

Steps to reproduce:
1. Build a room of any size, with one wooden door.
2. run, /effect @a glowing 9999 255
3. Inside the room, run the command, /summon Zombie ~ ~ ~

4. Leave the room, go into survival mode, and the zombie will not chase you, even though it should.