Mouldy, if you allow me, I would try to make it clearer what that musician wanted to say when talking about sneezing to let your voice be emitted freely, etc. I think the term is YAWNING and not sneezing. If this is what he said, it is absolutely true (according to several serious teachers and books I know) because when you yawn you get your larynge in the most relaxed position and the upper (most internal) palate in a high position, allowing for the formation of a large cavity in the inner mouth.
It is a known trick of the teachers to tell you "get the yawning sensation" to make us feel the correct position for a maximum flow and minimal effort. Those who learn to manage muscles to obtain this effect, do not need to yawn - they start to sing with their real voice. At first the sound is strange, feels too artificial, but so is this business, to look for beauty in the artificial fact of making music with an instrument that has been made up to speak, scream, curse and drink gallons of beer (oops sorry ladies, of course you don't curse).
Un abrazo - Andrés