Mmm, when I think of him, I tend not to draw a stark line between "real" (internal) vs outside-facing so much. Of course he has a filter, but I believe he is able to be so consistent in tone and message because the core tenets of his "inside space-kitten world" and "outside self that we see" are generally in sync. He has mentioned that conversations with the media (maybe some more so than others, such as Shuzo-san, and certain times more so than others, such as right after competitions) serve as external stimulation to help comb through his thoughts / his own processing of events.
Perhaps because he's done this for so long, he seems to have come to use those opportunities to establish what he himself thinks, perhaps unlike your usual athlete, who'd be busy trying to come up with something appropriate for the occasion. In this way, Yuzu's many different "selves" seem quite in sync with each other. Another example I can think of is during press conferences. I don't think he immediately puts on an "outside face" so to speak after he competes. Press conferences, maybe due to the mix of adrenaline rush and HisGreatEnemy!English, is often where he is the slowest (but still machine gun talk). He hums and haws quite a bit, occasionally going back to correct himself. His infamous 5-minute-long response to "How many quads would it take to win" from NHK 2015 was especially slow. He was deliberating words, but everything came out extremely clear. And based on how he's behaved all throughout these years, that's his true belief and what he practices.
So, while he has a more private side we sure don't get to see, I think that side has the same core beliefs as the "outside face" ----> hence consistency.
Sorry, such a ramble and not exactly making sense either.