Because of the pixel belt change of .17.
Does this mean the miniloader is unable to keep up with Extreme Fast speeds? Your info page says it's limited to 120 items/sec. Is that still true? In .16, that would mean it can handle Extreme Fast belts at 7200 items/min. With .17, it looks like that has been bumped up to 135i/s (according to ingame tooltip).
It seems .16 Ultra Express did 160i/s. But .17 now states 180i/s. Which is right at your max throughput listed. So is it safe to assume that's still accurate?