Well, both of you are right, in your own way!

For the SC, well, there's that funny reason! And it depends on how strict they wanna be. Obviously it's difficult to follow the 3 months thingy due to work, etc commitments right?
For you, you are right when you said that you have only used so much. But try to follow the every 3 month rule tho (for warranty purposes). Even yours truly when i had my kancil, as most of the time @ LRT station, my problem was like yours. Although I didn't really want to change, at the end, warranty mattered more. After the warranty is over...

For me, as i'm driving a FIAT, am on Selenia 20K, so i only change the engine oil once a year, as i'll hardly reach 20K or even 10K a year! But I DO change my oil filter regularly every 3 months or so...
The idiots @ Torino even though am using 20K will STILL tell you to come and change every 3 months! Dumb!!! But most will tell you, if you're on fully synth, you can stretch it BUT change your filter regularly...

Just my opinion.