Thanks for the suggestion. I think you can use notes for this. So if you have a fuel-up you don't want to be part of the record—but you still want to record the details—add the details as a note. Notes are not included in your fuel-up data. You might have to click "missed a fuel-up" once in a while, but otherwise it would work the same way as an official "don't track this fuel-up" feature. So the data is there, but not part of the statistics.
You're not alone, we recently had a similar discussion
here. The conclusion we came up with there was to just skip entering the fuel-up if you don't want it to be part of your statistics.