Speed Ruts

Certain PEOPLE have written (not on this board, but in texts) about students "digging themselves into speed ruts," because, for example, they are writing 60 wpm and continue to write at 60 wpm rather than PUSH themselves to 70 wpm.  By staying at 60, they supposedly drive themselves into a speed rut from which it becomes more and more difficult to escape the longer they remain writing perfectly good outlines at 60.
Somehow that thinking seems completely wrong to me.  I somehow think they'd get faster over time even if they don't force speed.
Does anyone have any comments?  Any EVIDENCE either for or against?

(by shorthandmarc for everyone)