*BANG!*
A lot of spells have abridged versions of their cast, like shortcuts that can help the caster get them out faster.
It takes a lot of skill to accomplish and it's easy to mess up. As is usually the case with Magic—especially the act of condensing magic—messing up usually results in a backfire that can destroy the Mage from within. So again, it's a skill only used by skilled Mages.
The thing is though, the caution is only really directed at normal Mages who rely only on spells and thus cast large spells that are dangerous and insurmountably difficult to condense into shorter casts.
For Mage-Knights, simple spells are their bread and butter.
Why?
Well, first, most Mage-Knights venture into the practice in the first place because they can't perform the grand spell casting and thus decide to focus more on honing their bodies instead.
Second, because of the close combat way of fighting, there isn't the advantage of distance that normal Mages have to craft large spells.
