1. It was as I stated earlier. A major qualifier - and I'm not sure quite how to state this succinctly- but it is only an option for people who have an ADR.
2. A second major qualifier is that parties in this situation give up all priority as to when they will be seated. Most people do not want to wait 90minutes (past ADR time) to be seated, if they have a 7pm ADR, they want to be seated at 7pm.
I also presume that the policy could change at any time. Per the example already discussed in this thread: people saw they could park at CR for free, and that it was easy to walk from CR to MK. So now WDW has become very strict about parking at CR. Of all the hotels, CR is especially strict for good reason. WDW knows people try to park at CR to get out of paying to park at MK. During the pandemic, too many people were even getting dropped off at CR to gain a RD advantage, so then CR wouldn't even allow Uber drop offs at CR, especially in the morning.
3. Sure it can, because as I said above, #2 makes this a very unappealing option. Most people do not want to wait around that long to eat. You have said a number of times on this forum that your extended family is not able to wait long for attractions. If you make a 9am ADR, would they happily wait until 11am to eat breakfast? Would they happily want to wait until 9m to eat dinner? I know I don't generally want to do that.
I qualified my reply heavily to say I am sure it can't be done at every location, especially the ADR's that are hard to get. You are free to dismiss what I'm saying as, "CM discretion" and nothing more. To some extent that is true. As I just said earlier, WDW policies are often murky.
I am certain it is only allowed because to date- people have not abused this policy.
I also appreciate having a civil discussion here!