The quote is for real and it kinda looks like you didn't even read it. He never said it would "stop" anything, and he said it's a stopgap measure until the real improved sieges, which includes basically everything you proposed.
it isn't a stopgag measure. It is just plain stupidity, as he knows that it won't even meet his own short term goal. Doing something that you know is a failure before you even begin is certainly stupidity.
I know that, sometime in the future, Toady will improve sieging. But the odds are against him "reverting" the change to channeling at that point. People will be used to the new channelling system, and the user base will whine and complain and demand that he change it back, and who cares about clean breaching with just using the channel command, they can do that with mechanisms, or whatever has been added by that point. After all, it is an advantage to be able to designate from the above, and that feature will be useful in other circumstances.
His goal: Make it more difficult to prevent throwing up a one tile moat when the player is first ambushed. Change: Fail. People weren't using that to make their "instant" defense when something nasty showed up before the "real" defense had been built. Worse, Toady knew the change he was making failed on that point. Verdict: Stupidity. If Toady had changed channelling just because he preferred how it works now, or to give us making ramps down from above, then it would be a success. But to make defending harder? that's what his military changes have done. Made it near impossible for dwarves to defend themselves. It's certainly much more challenging getting them to do anything like they used to prior to the military enchancements. THAT will take new players much longer to master than "old style channelling".
I still like Dwarf Fortress, but I hope Toady puts more thought into his minor changes. The impact can be significant to players enjoyment of the game. Having fun while playing is why we play Dwarf Fortress. Having fun with DF is why we support its development with our money. Which is what allows DF to continue to be developed. I don't want Toady to lose that support. And if he continues to do truly stupid things, he will. We don't want that. We want Toady and Three Toes to have very long, very happey, and very successful careers and lives so we can enjoy DF as it evolves towards version "1".