Sprinkle is typically called for in kit instruction, to my understanding, mostly for it's simplicity. It will take longer for the fermentation to get up to full speed - due to smaller surface contact between the dry yeast and must - but it's a fool proof solution for would-be-vintners of all skill levels.
Re-hydrating will help the fermentation to get started more quickly. However, specific parameters may need to be met - ie. volume of water used, water temperature, etc. - which leaves some room for error.
Nothing wrong with the re-hydrating you've done, especially if your must is fermenting away healthy...