Depression or life schedules in general can really make things hard. He might well have tried really hard to make it work and just couldn't finally giving up. As someone with a youtube channel for 16 years who didn't post anything for the first time forever due to depression, but people still gave me money, that's back pay for the entire catalog of work I created. This isn't some massive corporation making these promises, this is an nobody like you and me, putting in tons of work and deserves to get paid for the effort put in to entertain us. As much as people might not want the novel he will almost certainly be giving out the novel as a reward to paying customers. The more support the person gets the more likely they are to consider returning to the AVN format after the story is finally completed or allowing someone else to put it into AVN format. I already got a lot of entertainment out of the really hard work and talent done. That alone deserves to be paid.
If a giant corporation did this, sure be pissed and raise hell. The amazing thing about AVNS is completely nobodies can make amazing CGI movie quality work with just one person as a side project. Sadly nobodies have everyday nobody problems just like the rest of us.
I do understand your side of transparency but as a friend of a disabled artist, the person is probably beating themselves up and feeling like a complete failure even more than any angry ex-fan which wont do a damned thing to make the AVN actually ever happen. Support works much better than abuse. I view bascially all of patreon as a form of encouragement to artists to do more of their work I enjoy, not a bound contract as an exchange that you'd BETTER GIVE ME! Patreon is a donation to encourage nobody creators. Nobody creators with nobody problems. If you think of it less like a purchase and more like tipping which is what it really is, its a lot more acceptable. I will still go back and read this through every few years, its something created and permanent. Whether its in a completed form has nothing to do with the work that has gone into it so far.