you should be fine on Snow Leopard. the HSTS regeneration only happens on Yosemite, and Mavericks i believe.
test it out with this page:
make sure to enable cache removal in your Cookie preferences.
Thank you for the response. It doesn't even generate anything. Come to think of it, I tested it somewhere else and it gave me a unique number, but when I went back later the number changed so I'm not sure there are HSTS cookies possible in Snow Leopard with Safari?