It gives me a clear opinion that the guy can bring in at least one skilled dev to clean things up for him
"oh crap, I forgot to close this 'for' and 'while' loop" or "oh I made a typo on this line", is how I picture him reacting and addressing feedback after every iteration he releases.
Your picture is quite far from reality of writing a code in a framework like with RPGM engine here. In reality as a developer in this situation you have a black box (about which you don't have even the slightest clue of how it works internally under the hood) with a lot of buttons and joysticks sticking out of it. So you have to waste a lot of time learning about all these "interfaces" of the said black box and trying what tinkering with them does. It's not a generalizeable developer skill and has to be "acquired" for every engine \ framework. So RPGM dev is RPGM dev, Ren'Py dev is a Ren'Py dev, Unity dev is a Unity dev... the list goes on.
For example modern RPGM engines are based on JavaScript language. But it doesn't mean that JavaScript knowledge (or general programming knowledge) translates into the ability of creating RPGM-based game, it's only a pre-requisite. RPGM-specific knowledge should be acquired in order to assist or review with the dev's code (and here we have an incredibly old outdated non-maintained deprecated version btw). In frameworks \ engines the basic programming language constructs are rarely used at all. And it gets even worse if the custom obscure solutions are used on top of it...
