I actually bought a gecko that was TSM at like 89 degrees and it turned out to be female. Which was quite upsetting it was a really nice gecko too. But i sold it didn't need a female.
I would tend to agree with Robin on this... With most species of animals, there are usually more females produced than male... So even when you incubate at high temps you will still produce females, just not as many as you would at temps of 86 and under...
I have produced females at male temps and they have gone on to breed just as willingly as females from female temps... They are no more aggressive or any less receptive to males advances...
+1, I think the only way you will produce a non fertile or receptive gecko based solely off of temps that it would have to be an extreme (either super hot or super cold). Nature is intended to allow for reproduction by all means possible, and I doubt that 5 degrees is going to dictate thousands of years of evolution.