That's true. What I really mean is that tracers are incendiary ammo, even though in nomenclature incendiary ammo and tracer are two distinct types. Really any tracer is incendiary, be it an antique wp round or a modern magnesium round. If you shoot a can of gas with ball ammo you're just going to put a hole in it, if you shoot a can of gas with a tracer you're going to make a fire.
I don't think the tracer ammo will ignite a gas can any better than a ball round. I saw an actual experiment on the History Channel a while back. I believe the gas caught on fire for both types of ammo. It was the vapor which catch fire and burns and not the liquid fuel itself. This would be the largest advantage of having self-sealing tanks. Self-sealing tanks may not self-seal as one may think, but they do prevent air pockets of vapor to easily ignite upon bullet strikes.
However, an incendiary round may only work if it gets lodged in a plane and stays there. It would continue to burn and melt other parts of the plane. If an incendiary round goes clean through a object it may not have anymore effect than a ball round. Many, many years ago I remember reading how Spit and Hurricane pilots would use different types of ammo in the same belt in hopes of downing a German fighter over Briton. The ammo could be a mixture of ball, tracers, armor piercing, incendiary, etc. An incendiary round may not take down a plan immediately, but it could stop a German plane from making it back across the Channel after catching fire.
I am just guessing and relaying a little from what I have seen and heard, but don't take my word as 100% true.
