Bill Tindall, E.Tn.
It is true that the LEL is greater than a concentration of vapor one would tolerate working in. But a LEL could exist where your nose isn't. That is the danger.
Lower flammability limit, LFL, and lower explosion limit, LEL, are equivalent.
"and the only place near the LFL is just over and in the open can."
While the container one is working from is a potential source of LEL that is not the area of greatest evaporation rate. The greatest rate of flammable vapor generation is at the application site. Not so much with a slow evaporating solvent like mineral spirits, which is why mineral spirits is used instead of naptha. But the application site is a significant risk with fast evaporating lacquer. Spraying generates a higher rate of vapor generation than brushing.
Another concern is the heavy flammable vapor sinking into a poorly ventilated area and concentrating.
Bottom line, the good ventilation needs to be where the application is occurring.