No, it's not such a silly question (I hope)
As far as I can tell, a model can move wherever it wants, with any amount of direction changes as long as it doesn't go over an impassible object up to its maximum move allowance.
So, the knights of Relan get a bonus if they move over 4", if they start 2" away from an enemy, is there anything stopping it from moving 3" back and then 5" forward into contact? Or just take a sweeping 8" curve into any model it likes even though the target is closer than 4" at the start of the move.
Should there be a rule that states that if a model gets a 'charge' bonus of any kind by having to move x", it must move by the shortest distance possible to reach its victim? Without it, there is no reason to give a minimum move distance.