I’ve just read this and I disagree with it somewhat.
The steeper the roof pitch, the lower the gutter should be placed. On roofs with lower slopes, gutters should be placed close to the roof’s surface.
In my experience with gutters that are placed too low in a heavy rainstorm the water off the roof flys straight over the top of the gutter making them useless. The only reason to keep gutters low away from the roof is in snow areas sliding snow can rip gutters off. But in those areas the likelihood of very heavy rain is somewhat diminished. ALso snow guards can be placed on the roof to protect gutters from this. All depends on the situation and areas.