Not that paradoxical at all: Meta-Battler is not Ushiromiya Battler, Meta-Beatrice is not Yasu. That’s part of Beatrice’s characterization, even; “who am I” and such. We also know that Forgeries are not completely devoid of manipulation because a Reader or Game Master can embellish elements (and if the message bottles are briefer summaries of tales, what we see by necessity must’ve been so embellished).
It is entirely possible that the meta-layer doesn’t exist at all until Legend concludes, bizarre as that might sound. Beatrice is literally revived by the “ritual” of the EP1 narrative, and Battler is literally elevated to the meta-layer by his challenge to her. It’s weird, but it’s the meta-world, which is explicitly magical and potentially nonlinear to a huge degree (Meta-Ange being contemporary with Meta-Battler, e.g.).
So basically: “Battler” as we know him is the elevated meta-construct of the Battler of Legend, who is a character in a story presumably written by the RL Yasu but not the actual “Ushiromiya Battler” who existed in Yasu’s real world (if there is any real world). Likewise, “Beatrice” as we know her was born from the possibility space of the witch being real as an answer to the stories, but with only as much information as Yasu imbued into her own characters; since she was deliberately obscuring that information, not even Beatrice necessarily knows everything about her source. The two of them then go on to engage other Forgeries/Fragments and Battler’s position there can be seen as almost a sort of secondary Reader to Beatrice as Game Master. The story is formed by their back-and-forth on the layer of interpretation, with tweaking pushes of the story taken by each (but more by Beatrice than by Battler).
The degree to which these Game Masters and secondary Readers choose to manipulate their roles intensifies in Chiru for various reasons.