Fluky thing happened this morning. My 60-day window opened for dining for DH and DD’s Run Disney trip in October. I attempted to book Le Cellier for dinner for 2 people. It did not show me any dinner times, so I booked a lunch. Then, on a hunch, I tried to book a second reservation for dinner, but this time, I changed the party size from 2 to 3 people. Lots of dinner time slots popped up. 
So, I booked a dinner time for 3 people. After confirmation, I tried to go back in and use the “Change Reservation” link to change the party size to 2. The system forced me through selecting a date again, etc., and again, and only showed me lunch times for a party of 2. I am guessing they have small, designated tables for parties of 2, and those tables were all booked? I’ve never had this happen before. I guess I will keep trying to modify, and if that fails, I will call the dining line. But most of the time, CMs can’t do anything different than I can do myself online. 
No real need to do this. Showing up with fewer people is no problem. As long as one person shows up, you avoid the $10/person no-show fee. Of course, you can still keep trying. Now that the cancellation window has changed to two hours instead of 24, many people wait to cancel until day of.
You are right, about them having different sized tables and possibly having all the 2-tops booked. It’s very common to look for a bigger size like you did.
I found recently they seem to have closed that loophole that let’s you downsize the reservation. It is frustrating they don’t have many (or in Wailulu’s case - no) 2 tops. I just book 3 and show up with 2 now. They are always flexible by 1.
I pretty much always book for a larger and/or odd number than our party number at booking
If another folk or two show up we can be accommodated.
Currently we might be 4 instead of 2 traveling but we may not know until much closer to departure day.
I’m either by myself or with one more person when traveling to WDW. Asking for reservations for 1 tend to come back with zero availability. Most of the time, asking for reservations for 2 also tend to come back with zero. Reservation for 3 yields lots of availability! When you check in for your reservation online, it will ask you how many people will be dining. It has never been a problem to show up with less people than what was on the reservation.
I used to feel guilty when I made a reservation for 3 and it was just me (myself, and I would make 3!)! 
No need.
This is very common and extremely maddening. Like, if you have room for 3 you have room for 2 
And one could argue that they are trying to fill every seat in the restaurant but what we all know is that in recent times the restaurants - even the very high demand ones - are rarely completely full.
Just show up with your party of 2 and check in. As long as at least one person shows up you are not charged the per-person no-show fee
I’ve known people to have no issue with much larger parts of their group not showing up. I joined a friend not long ago who expected 5 others (well 4 plus me) but the other 4 bailed for various reasons.
No problem
Just chiming in to agree with the others. As a local I always book 3-4 for just 2 people and then when I check in either on the app or in person I let them know there are just 2. There really is no reason to try to modify 
Agreed with the others. If you do online checkin, it will allow you to check in for any number up to 1 more than your reservation. If you check in in person, you usually have even more flexibility. I have never been charged a no show fee as long as at least one person shows up — including if you tell them you changed your mind and aren’t dining there anymore!
Thanks all!