Ehh...I don't know if I agree with this method. Granted, there are some places (like Kona, which you mentioned) where you should be okay if you do this and in fact we have when plans changed last-minute. However, an example of where this doesn't work is when DH and I tried to quickly make different plans when we got to Rose & Crown last trip and saw that their menu had totally changed from what the website reported (at that time, it was very similar to our last experience and we loved it, so we were really looking forward to this meal). It was so disappointing. We ran around all over Epcot in the heat, trying to find an alternative, only to be turned away time and again, and wound up sticking to R&C (worst meal and service we had all week, no doubt).
I know everyone's different, but speaking for myself, when I go to WDW and spend $$$ to be there, I want to know that I'm not just going to have to take whatever's available on the spur of the moment. And most places have such a nice array of menu choices, I can decide if I'm in the mood for fish, beef, chicken, pasta, whatever once I'm seated.
Just keep checking, there's so much time between now and then, lots of people change ressies every day. Something's bound to open up for you!