I had a look at the Tranquility Base website. There are several definitions of 'Snowflake'
It seems to be trying to sell mugs with a definition of a word on the side.
Looks like anyone can give their own definition of a word, so don't really know whose definition it is.
Here's another one:
"An insult, used to mean that a person is too easily insulted or is too sensitive to the opinions. Mainly used by Alt-Right Trumpet blowers, who ironically, don't realize they are the very definition of the insult they love to throw around. Snowflake is used by people who are incapable of using their intellect and their words to make their point in an intelligent manner.
Look at that Alt-Right snowflakes pitching a fit over people they think do not sufficiently engage in flag worship."
(American spelling, not mine!)