Hmm. I'm researching a bit to help clarify this matter, and I'm finding that there are a few different variations on the shifting patterns for werewolves.

As I read in [@Polaris North]'s CS, it states that Will can partially shift, but it takes awhile for him to fully shift. In some wiki's partially shifting is experienced during a werewolf's puberty, but then it doesn't touch the subject of partially shifting ever again. For the alpha wolf, they have the ability to choose whether they want to partially shift, or shift in a matter of seconds. The ability implies that partially shifting is only shifting to an extent where fur, claws, and fangs are presented.  Though, the alpha is elite and more experienced, thus they have the ability to shift within a matter of seconds. Therefore, a wolf beneath alpha would suffer from longer shifts, all depending on the experience of the wolf, which is usually defined by their hierarchy within the pack. Elder wolves, Alpha wolves, and possibly beta wolves, will have much quicker shift times based on their experience.

So I'll have it that the Alpha can only practice partially shifting, whereas other, inexperienced werewolves will only be able to fully shift. Due to a young werewolf's rabid nature, they can't withstand and control the ability to the extent of not fully shifting when they do go to shift. Partial shifting is, essentially, forcibly shifting to an extent of great control with some added benefits of the werewolf form.

Arguably, Polaris has stated that he is a beta within the pack with lots of experience in shifting, so perhaps he's closing in on the ability to partially shift, but isn't quite there yet.

EDIT: definitely edited this while people were reading it, IM SO SORRY. AHHH.