I like having more literal translations available in combination with more natural localizations. So I revisited this scene.
「……なあ、リオン。リオンにとって、俺は今でも対等の関係じゃないのか？」 Patch: "...Come on, Leon. After all that, you still dislike me that much?" More literal: "...Hey, Leon. Even now, do you still not see me as an equal?" [*]
「それは…」 "That's..."
「俺はリオンの事、大切な友達だと思ってるんだけどな。」 Patch: "I consider you to be a good friend, Leon." More literal: "Because I think of Leon as a precious friend."
「なっ……！」 "Wh...!"
And of course, then Leon's usual "I hate people like you...!" tirade, preceded by annoyance at how many times he's had to repeat it.
「だがまあ……少しは認めてやってもいい。」 Patch: "But... Fine, I suppose I can make a small exception." More literal: "But I suppose... giving you a bit of recognition is fine."
So this scene is both Dymlos and Leon back-to-back indirectly letting Stahn know they respect him. It isn't just about friendship. Or rather, it's friendship hiding behind respect.
I don't dislike the change the patch made, to make it more overtly about friendship. Because the whole tsundere never-saying-what-they-mean thing can be easy to misinterpret if you aren't familiar with it. That's part of why I ended up disliking Leon in my first playthrough of the PSX version. His localized dialogue (from the late 90's, when hardly anyone even knew the term "tsundere"), and without any kind of voice acting to give clues through cadence, didn't make it very clear that he was a tsundere archetype and being dishonest whenever he was pushing people away.
So if they kept the dialogue as just being about respect, I could see some people thinking it was a begrudging admission that Stahn was someone respectable even though Leon didn't like him as a person. ... Well, if the rest of the game didn't exist, at least. They do make it pretty clear through a bunch of other scenes that, even if his head doesn't think of Stahn as his friend, his heart sure does.
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[*] HI, THE TERM 対等の関係 ("equal relationship") IS DIFFICULT TO CONVEY. It's neutral in that it can apply to any relationship, whether it's professional, platonic, or romantic. It is basically the opposite of a hierarchical relationship, but also isn't used exactly the same way as one would say "we're on equal footing" or "we're equals", because it can apply to things like professional relationships where you are not actually equal. It's like being able to tell your boss when they're wrong and them accepting it as good critique.