The article you read is correct. I'm running my motor at 12x rated voltage now.
The calculations shown is the 'steady-state' current, i.e., the coil has been switched on for some time. The motor coil (inductor) will resist the _initial flow_ of current when switched on, thus the higher voltage will speed-up the process. Subsequent to this, the inductance effect reduces because current already flowing; this is when the power resistor come into action to limit the current (above calculations).
I'm no expert in the subject so other Gurus here may explain to you better. You may want to read the white paper at
www.geckodrive.com for some additional info.
Another informative site (Warning: Nice charts but lots of maths
)
http://www.cs.uiowa.edu/~jones/step/current.html Check out Figure 4.2; specific to your question above.
Regards,