I just got m3 version. I know that this version has considerably slow SSD compared to i5/256GB. But seems like mine is lower than usual. I would appreciate inputs from anyone with m3 version.
Yeah, those are slow results for sure. Have you checked your hard drive disk drivers? Tried perhaps uninstalling / reinstalling them? Stupid question here - but have you checked the benchmark results online with other M3s? If so, what did you find out? Considering non-SSDs run at a max of 95Mbs on a good day, your results aren't horrible when compared to this, but still, your results seem painfully slow. Take a look at this post which seems to touch on the M3 SSD Issues - There is also a "hotfix" link available there- perhaps this may help you.
Additionally - here are some pics of my SSD Results using Samsung Magician on a SP4 i7 - along with the driver information for mine. I know this may not help you at all - but perhaps you can deduce something.