Doesn't a party of 1 get the same size table as a party of 2? Have you seen any tables in any restaurant for one person?
My thoughts exactly. I have never seen a table for one. Usually there is a table for two and they may take away one of the chairs, so if you are a single, expect to be seated at a table that can seat two. It isn't cheating the system or anyone else to book a two person table.
Just like a three person group will be seated at a table that can seat four.
Also, I found I couldn't get all the ADR's online when my 90+10 day opened up. Yak and Yeti wasn't available AT ALL, PERIOD. The other TS I got were not exactly at the times I wanted, but close. I called by phone after about 45 minutes of frustration and the CM was able to get me Yak and Yeti (she didn't know why it wasn't working online) and she was able to change the ADR's I got to times closer to what I originally wanted.
Since you are out of country, I realize this may not be an option to call overseas. But my point is, the online system has a LOT of flaws. You are going to have to work around them. I am an honest person but taking a "two" person ADR when you are a single is NOT cheating ANYONE! As mentioned, if you could get a CM to make the reservations for you, you would still be seated at the SAME size table, the second chair may or may not be there. They can easily take that second chair away and set it aside or use it elsewhere for a larger party if that makes you feel better.
There are rules (which are rigid, everything in life is black and white) and there are principles - whereby you try to do the right thing in a given situation. I think you are trying to do what is right but carrying it a little too far. Book the two person ADR's, NO one is going to find fault with it. And on these boards, if anyone thought you were doing wrong, trust me, you would definitely hear from them. (no flames please, I don't have anyone in particular in mind)
And regarding what to say when you check in, just tell the CM the truth. The system would not let you book a single so you had to book for two. They will understand and it just won't be an issue.