That's odd, since CR #7 is a replacement effect. I guess they had to clarify that it is a replacement effect.
CR #7 is exactly what is being changed. The new rule will be the little quoted excerpt I included in the first post of this thread. If a commander is in a graveyard or in exile since the last time state-based actions were checked, its owner may put it into the command zone.
Players who didn't closely follow the rules and who just learned that you could put the commander back into the command zone sometimes missed the significance of the fact that this had implications for "dies" triggers. People would build Child of Alara decks thinking that you could kill your commander to get its trigger, but still send it to the command zone. You couldn't. Only now, with the rule changing, you will be able to.
Elenda is newer, but might be an even better example. It's a lot better as a commander if you can get the "When Elenda dies" trigger and
send the card to the command zone. But CR#7 didn't allow for that. Lots of players, including a member of the CAG, assumed that it would work and wanted it to work.
It goes the other way too. Under the old rule, if I had something that triggered from a creature dying, I'd be incentivized not to use it on commanders because my opponents might just send them to the command zone as a replacement effect. And because commanders are often important targets to kill, this made cards with those triggers artificially worse than they really could have been.