Defensive line alignment is a lot more than just where a defender lines up before the snap. The technique and shade can completely change the blocking picture for the offense
Moving a defender from a 1-technique to a 3-technique, from a 5 to a 4i, or even just changing from head-up to a shade changes the offensive lineman’s angle, first step, leverage, hand placement, combination possibilities and path to the second level. The offensive play call may stay the same, but the geometry of the block is different
That is also why understanding gap and technique numbering matters. A 0-technique, 1-technique, 2i, 3-technique, 4i, 5-technique, etc. each creates a different surface for the offense to block. Those alignments can influence where double teams come from, how long two blockers have to stay connected, which linebacker stays clean, and how quickly an offensive lineman can climb
It carries over to the pass game too. Front spacing can change protection sets, stunt angles, twist opportunities and how the offense sorts pressure
For defensive linemen, the goal should be to understand more than just “I line up here.” Know why you are aligned there, what gap you are controlling, what block you are trying to make difficult, where the help is coming from and how your alignment fits into the entire structure of the defense