I think you'll find that the AIP is no longer a document that sets standards. It's intent, at least under the new CARs, is to explain and clarify specific rules. You don't always need to take the reference to a "180 degree turn" as gospel when drift correction is involved.
This is confirmed by another part of your quote that talks about a TRACK. You use whatever heading is appropriate to maintain that TRACK the best way you can. With correct anticipation of drift after completion of the turn, you may find that you roll out of the turn after something more or less than 180 degrees of turn.
Take the example of a R/H pattern with a +20 degree drift angle set on an inbound course of 360. Heading will be 020. To track outbound on 180, your heading will be 160. Total heading change is 140 degrees.
The same setup with a -20 degree drift angle on the inbound course means a heading of 340. Outbound heading should be 200. Total heading change is 220 degrees.
In each case you will maintain an outbound TRACK that is 180 degrees different from the inbound TRACK. The only real difference is that the outbound track is a DR track.