My interpretation (as well as at least one FOI I know)
And thats the problem Krusty. Not that you have an opinion, but that the FOI has his/hers and seeks to impose it on operators. This is where the whole regulatory system breaks down, it has human beings in it
I believe this is the reason for the ATOG clarification.
As to why it isn't done more often; I'd suggest that its mainly because operator's haven't needed to in the past because the established practices worked.
In accordance with CAR 5.40 an FO can log ICUS as long as they meet the requirements of the CAR and as long as the operator approves it. The fact that operators are unlikely to approve it in most cases due to CASA pressure or industrial pressure doesn't undermine the reg. I'd like to see CASA try to take action against an individual or company for doing it, the reg is clear.