I think side spills are actually necessary, otherwise in pitch dark environment you'll have trouble. That's my experience from camping: using a Maglite when camping, with the beam set to the tightest, everything else not in the beam range could hurt you (as it's too dark for everything except what you intended to see). You shouldn't focus on the target alone. So I would say, we normal people do not have any legitimate reason to have a beam without any side spill, because side spill saves us.
The only 2 situations you want to have no side spill are when you want to pinpoint something in a long long distance (so you need a super tight beam without any side spill to have a real long throw, like turboheads do), and when you do not want to reveal your location in darkness. Both are special tactical situations (although for long throw, hunters may need it too). Even when in real tactical situations, you still want to have side spills even though you have a tight beam (for LEO's, that's to make sure they don't shoot the wrong guy, directed the beam to enemy's face or not).
And for aviators, do you actually think they can check the equipments without side spill? Think about it: seeing the big pictures is always the best way to locate errors; if you have a no side spill beam, how can they make sure every little part is checked? You may miss some; that's the whole point for side spill: not to miss anything important which isn't in our target range. So I would say, if A2 has no side spill, then it will not qualify as a light for aviators.
Therefore, Surefire's lights, except the KT turbohead series, are designed to HAVE side spills. KT conversion kits are designed to have no or little side spills for long throw, although many reviews in CPF said they're not too good. And I believe except Inova X1, no lights will actually not reveal your position.
That said, if you want to have a light with absolutely no side spill, that's a little extraordinary, and I think only the streamlight TL series may be able to do that, if you don't want to go for turboheads.
Mind you, though, L4 is designed to be very flood, it cannot throw far. So for something that A2 can shine from a certain distance, L4 will not do any good. I think, for aviation purpose, L4 cannot perform well.
Just my $.02