I'd still say it's spontaneous because when you reduce pressure you're removing a factor rather than adding one. It's like saying "when you compress a spring and then remove the compression force, it will spontaneously return to its previous length." Water vapor can be seen as water's "natural" state when thero no pressure forcing it to be a liquid. Also saying "simple thermo" to an astronaut is definitely mansplaining, because it implies the other person doesn't know that simple thermo.