I think the important thing is that we figure out what works for us.
The tiny difference of whether a ruler is used to be cut on the line or next to line was discussed a lot back in the starting days of rotary rulers. The different ruler companies actually said whether the line was on or next to... It may seem like a tiny amount but when you duplicate it across oh, a hundred 2" squares, it can add up.
Likewise in terms of adding up, every seam variance is doubled (or halved) by virtual of being 2 pieces. So with one piece the seam is only 1/8" inch off -- but with two pieces that adds up to a 1/4" already!
I find my sewing seam variance to be more of an accuracy issue than my ruler...
I tried to be very precise in my early days of quilting, with cutting and seaming and so forth (grain line!) and spent many happy decades with those techniques. Starting a tiny bit around Y2K, and pretty constantly for the last 10 years, I've been a big believer in cutting large and trimming down as being equally as fast and more accurate for my work style.
That rounding up the HST is a big step in the cut big/trim down thing. For me it was also triangles, but tiny ones the last time I pieced them traditionally instead of the square with the line down the middle...