Another thing to note is that the turbulence penetration speeds are for
severe turbulence. e.g. +/- 25kts IAS or more, "forced against straps", "momentarily out-of-control", blah blah...
If you encounter turbulence like this, then keeping the speed above the stall and below Vmo/Mmo could be regarded as a major achievement, so aiming for turb. speed is a good idea.
If you're
knowingly penetrating an area where such conditions have been reported, then whatever the manual says... But I think most of us would do our level best to avoid it, if possible!
(I get, well, not
annoyed, that's too strong, more
when people slow down at the first little ripple - if you're that worried, why not do the entire flight at turbulence speeds, just in case?)