Some people can only work alone (like some craftsmen). It's more complicated to delegate certain parts.
And sometimes it can take extra time, explain what you exactly want, check, correct, ...
Finding someone you trust to help is not easy.
It's his first game, he's got a perfectionist side to it so ... he won't want to give up too much what he thinks is important.
L&P explains that CS and RS represent 85% of the work. In fact I think that the script represents at least 50% of the work, because the structuring of your story will give the kinetics of the images.
I already worked on Renpy scripts, you spend hours and hours building, testing, correcting, testing. The pace can be less than 100 lines per hour depending on the complexity (nb of characters, paths, point's system, proportion of kinetic parts...) and whether English is your native language or not (L&P is German).
Someone who would be reliable would be someone who above all had a lot of patience.
version 0.115 ~ 3300 lines added in the script, theoretically 33 hours (at 100 lines per hour), but I think
in his case, ~40 lines (build, test, ...) per hour is closer to reality. And it's really difficult to spend more than 5-6 hours a day on this job (You need to take breaks from thinking about other things).
Here, almost all paths are linked, unlike many games, it is impossible to make a choice with a character without having a significative consequence on another character.
In a lot of games you say "Stop her/him" or "Not interested" and you don't get the scene it's inconsequential : $character_end = true
This is also why this game is different and interesting.