flammable: "easily set on fire; combustible; inflammable."

inflammable: "capable of being set on fire; combustible; flammable."

[Standard boilerplate about dictionaries being imperfect reflections of what words actually mean.]

[Perhaps less-standard boilerplate about how words can mean different things in different places.]

Whatever the nuances are, "inflammable" doesn't mean "fireproof", which is my main point.