I'm gonna always believe fourth meant it, to what degree and how serious he was, can be debated but he meant it one way or the other because fourth usually doesn't think 10 times before saying something and then he was looking in all directions except at gemini while speaking
And the moment he said it's about 2 people who already know everything about each other so they don't have to waste time flirting with each other, they can directly be faens, i swear gemini had the same thoughts as we all did