According to the data sheet and usermanual you only find two sentences with interesting informations
Searching in the data sheets/user manuals of the 7000 and 8000 for eventually more, nothing...
8000 "says" the same and in 7000 the hi-res mode is not mentioned..

Checked at last the DS1000Z: Same as 5000.
A few pages further down you posted some more screenshots with similar results:
Today, with the knowledge I got now about it, I would do the tests in a different way.
The test with the squarewave is good and can repeated when it´s interesting to know where the bandwithlimit lies.
Next could be a test like I did one, two weeks ago with a very small signal to see an improvement against non-hires mode.
Assuming the same method is used, I can test it with the DS1054Z at work next week.
But best would be testing with the 5000 itself.