Curate, connect, and discover
(Edited to adjust my argument).
I think RTFA confirming that Miles Edgeworth didn't intentionally forge evidence aligns with his established character in the first four cases. It does take away some audience interpretation but personally I'm fine with that.
First of all I don't think the rest of AA1 ever confirmed it one way or the other. There are a few instances where Phoenix thinks of Edgeworth as an evidence forger but it's not like Phoenix would know for sure either. (Do correct me, with specific lines please, if I'm wrong though).
But more importantly, if you only look at the first four cases of AA1 Edgeworth being an evidence forger doesn't make sense with his character. Why would a prosecutor forge evidence? Not including reasons like being blackmailed. 1) If they don't care (enough) about the truth (prioritizing things like success over it), or 2) if they truly believe the defendant is guilty and are desperate for a conviction (aka the reason Adrian Andrews forges evidence in 2-4).
Does Edgeworth care about the truth, before the start of his redemption arc at the end of 1-3?
Yes... kind of. I don't think he prioritizes the truth or consciously cares about it. As the "Demon Prosecutor", Edgeworth cares about justice, and achieving it through punishment. However, convicting the wrong person would not be justice to him. Which is what makes Edgeworth change sides to convict the right person in 1-3. So in that sense, he does care about the truth.
You could argue that Edgeworth had already lost once to Phoenix and thought "screw this, my perfect record is already gone, another loss wouldn't change that fact". But compare him to two characters who are actually obsessed with their perfect records. Manfred, a perfectionist control-freak, getting a penalty (not even losing!) unraveled him so much that he killed Gregory in the heat of the moment. Franziska after losing in 2-2 declares that: "That spirit channeling trial was a sham! I refuse to acknowledge its legitimacy! It did not count!" She doesn't even want to admit that she lost. Edgeworth, on the other hand, doesn't act like someone who truly prioritizes his win record over the truth.
Because Edgeworth didn't just let himself lose in 1-3, he made himself lose. He made Vasquez testify again. She would have gotten away if Edgeworth didn't say anything. And after the trial he tells the judge "Will Powers was innocent. That he should be found so is only natural… not a miracle."
Okay but if Edgeworth does care about the truth (to some extent), and believed that every defendant being guilty was the truth, he could have easily gone down the path of forging evidence to ensure the verdict reflected what he believed to be true. That leads me to my next question:
2. Does Edgeworth truly believe that every defendant he prosecutes is guilty?
Actually no. He says this in Turnabout Sisters: "Innocent"...? How can we know that? The guilty will always lie, to avoid being found out. There's no way to tell who is guilty and who is innocent! All that I can hope to do is get every defendant declared "guilty"! So I make that my policy.
Yeah I think that line speaks for itself.
Miles Edgeworth can't bring himself to consciously care about or prioritize the truth, but the moment it's presented in front of him he also can't bring himself to ignore it. He doesn't think it would be just to knowingly convict an innocent person, but he's so disillusioned and distrusting of people that he's lost faith in finding the truth.
So, he commits himself to getting guilty verdicts because he believes that's the best shot he has at enacting justice, even if he accidentally convicts innocent people from time to time.
And to me that aligns with his reaction to finding out he unknowingly used forged evidence in 1-5. Edgeworth was so disillusioned with finding the truth that he has accepted that some collateral damage would inevitably happen as a result of his mindset. However, because he still can't let go of his dedication to the truth, he wouldn't want to lie or rewrite the facts to achieve his verdicts.