@Paul *******
, come to think of it I DO remember reading a post somewhere that the FIRST time you get an extension from any Non-Imm visa (O, O-A etc) it has to be for the reason you got that visa. (which in your case was because you're over 50-retirement)
A guy had a 90 day single entry Non-O visa based on being over 50 (which he got from a thai consulate that still sold them), He got stamped in for 90 days and then during that time he got married and when that 90 days was up he tried to go get the year extension based on marriage,
BUT
he was denied because they said he had to get at least the first extension for the reason the visa was issued (in his case retirement) and then after that he could change the reason for the extension to something else.
That could be the reasoning up at your immigration office..