When a task is done just for practice.... like in 7.21, wouldn't it be a good idea to say that in the solution guide?
Sometmes when it is a tricky lab these can create confusion, as you scratch your head thinking "why is that there...?"
I get the concept of drilling, but at least say that in the SG.
BTW: An alternate solution could have been
Keep AP Path manipulation on R3 (as per Solution Guide) and then on R2 put an In-bound Route-map to change the ORIGIN to IGP. then no cinfiguration oon R5 would have been needed.