hebele I am not sure if I want to follow Faber 3B after finishing AIO2. But I think I should get it just to pick and choose pieces like this one.
From a performance perspective, 3B isn't necessary, the AIO and 3B cover the same ground in this respect. From a theory perspective, it's probably necessary depending on the student. The AIO series leaves out too much theory (and explanations) while numbing the brain with the world's most horrible pieces to practice.
I would suggest that if you have a solid grasp of the theory, then 3B isn't necessary. But, if you have any gaps, then either go through 3B strictly for the theory stuff or pick up an early intermediate level theory book to ensure you are where you need to be and move onto the next level in the Faber regular series.
Currently I'm getting help with the theory stuff from another source besides Faber. Simple things that Faber doesn't tell us - like the V7 chord is pronounced FIVE seven - and why the chords progress like they do. It's slow for me because I don't have a sufficient background in theory, thanks to Faber, but the internet helps fill in the gaps. Gaps like; is the F in the G7 chord Natural or Sharp? (It's Natural in the G7 but sharp in the GMaj7 chord. Yeah, go figure.)
Anyway, assess where you are and if you have a solid grounding in theory, and can play Canon in D at the end of the AOI, then 3B isn't necessary.