This matches my experience.
I have a 32" TV and currently watch at between 6' and 12'. I was one of the 400 people involved in the Freeview HD trial about 4 years ago and at the time when my viewing room was different but distances were similar to that I have now.
The BBC tech guys pushed a number of changes, resolution, bitrate etc at us for us to comment on. Some changes were obvious, such as SD/720p/1080i as the box reported these, but others, such as bit rate changes, and upscaled SD or 1080i/p source over 720p and vice versa were invisible to those of who were not monitoring the feed via a third party decoder.
Once in a while, we were informed that some changes had been made and we were asked to comment on what we were viewing. Some changes went unnoticed, so I cannot comment on what changed, but others were obvious, although some only under close inspection, forward of the normal viewing distance.
I would say that, based upon my experience of our 32" LCD TV non FullHD tv, what is now deemed to be a small screen, the graph is pretty accurate.