I have programmed in Ren'py and I have not found the "built-in support for branching" that you are speaking of. The challenge is more in keeping the paths straight as far as writing them so the dev doesn't screw it up. Each additional path adds an added degree of difficulty. Initially, the paths were only slight deviations, but the dev has made it clear that they will be full-blown paths in the future, so it is a lot of work, despite opinions (of non-game developers) to the contrary.
EDIT: There must be a lot of raw faces out there from all the facepalming going on. Heh heh. You're welcome.
Well, I didn't bother going through it's script, but at this time, from what's effectively in the game, he use the keyword "menu" to display the choices, and then "labels" & "jump". Since the karma's not doing anything, I doubt there's even a variable check, and even if there was, that's just an "if" to add ^^ There's nothing complicated, and i'm pretty sure it's one of the first entry in the Ren'py tutorial ^^
The only thing where I could agree, is that in theory, while writing the story (He should be writing it before "coding" it in Ren'py, if not, he's plain dumb, I mean, an architect make a plan before starting to build a house, right?), it's should be more complex if you want to have choice that effectively affect the story (since you can forget about it since you're not likely writting the story in one go^^ and then you lose consistancy), but it's not the case at all for now, and then it still doesn't have anything to do with "coding" (Since once the story is written, you "only" have to follow your own script, granted you can make a few mistake, that's why it should be tested & corrected, but that process can't be taking month like some excuses he gives).
And by the way, it's not (look at the spoiler down there), but let's say it was somewhat difficult.. He's been at it for more that 3 years.. You can't possibly say that he's could still be unfamiliar with it right? I'm pretty sure that even a kid who just learned to write and read could understand/do it in less that 3 years. (Since you don't even need to know how that work, just what the label and the jump keyword do).
You may really think that and not trying to troll us, and obviously there's always people that denigrate a work/dev that does his job for no reason(or just because the game doesn't go where they want), but there's nothing to say that can "clean" Irphaeus of all the half-assed excuse and lies that he makes up.