Tweener isn't about size as much as it's about skillset relating to size.
Never heard Donald spoken of as a tweener. His scouting report is all about pointing out that he is simply a player, and his size would not hinder him. They talk about his stature creating natural leverage, and about his extremely disruptive he would be in the NFL. Sorry, Walks, not a tweener.
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Tweener: Physically
between the prototype for positions.
Tweener does not mean the player isn't or can't be a great player.
Obviously from a skill set perspective, Aaron Donald was an obvious fit as a 3tech in a 4-3 defense.
It's the same with Odighizuwa. He is an obvious 3tech in a 4-3 defense.
Interestingly, like Donald, Odighizuwa will play in a multiple front defense and will play DE in 3-4 sets.
The 3-4 is actually a method of making 4-3 DTs and 4-3 DEs into better run defenders on "base" downs.
4-3 DEs become big LBs against the run.
4-3 DTs become big DEs against the run.
On passing downs those players move back to their positions on a 4-man DL.