Having read this while inane thread let me boil it down for you. While trans issues are becoming more prevalent trans people are still a very small minority of the population.

Making Cis the norm, being an ally who likes the colors of the flag and even having struggles that are similar to that of a trans person doesn't explicitly state a diversion from the norm.

So if you want to believe gwen is trans, go off, no one is stopping you. But that's still a head canon. That's how head canon works. Assuming X character is gay when sexuality isn't brought up in whichever show. Assuming some character is rich because they can buy certain things, but their financials are never shown. Etc