Personal anecdote: in my first year of college I took a Probability & Statistics class alongside Intro to Electrical Engineering. When I say "alongside" I mean they were scheduled in the same time slots. The registrar's office somehow didn't catch the scheduling conflict. I ended up only attending the EE lectures and I merely turned in the homework for the other one.

When the final exams were also scheduled at the same time I contacted the professors; they refused to let me reschedule since I didn't have an excuse that adhered to class policy. I might have failed one or the other if my grade in P&S hadn't been high enough to skip the exam—a circumstance I hadn't prepared for but worked out well enough.

For years after I graduated, though, I had recurring nightmares about needing to take final exams for university classes I'd signed up for but forgot I was in.

Anyway, I think the reason Emmet wears that apron isn't for protection or pocket space but to push his center of gravity back closer to his spine. Otherwise he'd have to continually lean back when he walks and that would probably make his back hurt after a while.

An unexpected piece of Emmet fanart by  bluecardd!