There are a couple of problems to waiting and doing it on the phone -
CRT is extremely popular.
October 27 will be the day everyone who wants reservations up to April 26 is going to be either on the phone or trying to book online.
I would imagine that someone who scored CRT online early wouldn't want to give it up to wait for the phone line to open.
However, there have been a LOT of problems with the online system not recognizing that guests trying to book a prepaid reservation are on the dining plan, so they've had to pay the full price in order to book online. They can always book at full price and get a refund when they arrive and say they want to pay with dining credits, but I'd imagine that most folks don't want Disney holding their money for up to 180 days before it gets refunded. The best they can hope for is that the system works the way it's supposed to and retrieving the resort reservation at the time of online booking will also retrieve the dining plan information. If it doesn't, and they try again and it still doesn't, the only way to get a refund earlier than arrival would be to have a phone agent cancel the current reservation and rebook it with the dining plan information entered (which might not be possible given the popularity of CRT).
Waiting for the phone line to open gives the online guests a jump on you - and on October 27 it will probably be a bear to get through to WDW-DINE anyway unless you're one of the first callers through. It's definitely a catch-22. If I wanted CRT really badly I'd just plan on paying the full price for it, book online and get a refund upon arrival.