On further investigation:
The paragraphs in the STM relating to the "booking downgrade" do not have the vertical line against them. This appears to indicate that these particular paragraphs are not new and have been there for some time.
Not nice but not new. The question as always is how or whether it is implemented (see White Knights post).
1.1, 1.2 and 1.3 are all, I would suggest, to be expected and not unreasonable.
1.7 simply clarifies the use of the ticket.
Further to my previous post, the question becomes what happens if you decline travel having checked in and/or accepted a Y boarding pass?
IMHO, I think I'd be waiting at check-in if there's a chance I'll not be travelling.
Thoughts?