Sure, it's fun to joke about all the crazy shit that Tumblr thinks up. Too many people have tried to hop on this 'I'm special and unique and different labels than everyone else' but I think it is important to realize that there is a reason for the distinction from gender and sex in the first place.
The big problem was that people were (some still are) using biological sex as a determiner of what a person's gender should be. The change in view point is that if the body doesn't match the mind, then you shouldn't force the mind to adapt to the body. From what I understand, this has been shown to cause mental health issues.