In AI CC 2018 and 2019, on Windows 10 Home 64 bit, the black border of artboards overlaps the top row and left column of pixels in the image when zoomed to 100%. (For 2019, Pixel Preview must be on to properly see this because of https://illustrator.uservoice.com/forums/601447-illustrator-bugs/suggestions/35736118-100-view-is-not-100-for-pixels-in-cc2019)

The attached screenshot shows a 16x11px artboard zoomed way in on the left, and at 100% on the right, plus an 8x version I added so it can be seen better. Clearly part of the white outline is obstructed by the the black border of the artboard. Not good!

So, basically, it's impossible to preview the full graphic at 100% pixel size. This is a big problem if you're say designing 16x16px icons where 31 pixels or a good 12% of the image is obstructed.