I think that it makes more sense to look at MrSL's track record than to compare him to some random other developer.
He has delivered 7 updates after the initial chapter 1 over the past 3 years. The time between updates has consistently been 5-7 months. Each update has been of a significant size - 10000s of words, 100s of images, multiple choices and complex paths that stem from your previous choices. The game itself has had improving quality, additional functionality and the addition of animations even back to previous chapters.
Out of all the developers of indie adult games, MrSL has proven himself to be one of the best. The game content might not be for everyone, but those of us who like this sort of intelligent and sexy gameplay REALLY love it.
It is not a quite as random a comparison as you seem to think. Iondivvy updated his first game also very regularly until the day he announced his second game. He told us that this second game would not impact development of his first game at all or just minimally. Hell yeah, what a complete liar and a... he turned out to be!
The next update after he started developing game two was feelable late and small, but he promised another update quicker and with more content. That was nearly a year ago and we still wait for that "fast" and substantial update. His excuses for the continuing delays (he announced another delay just a few weeks ago) are a joke and clearly fabricated to sooth the fans of his first game.
But "surprise", his second game is updated very regularly.
As said, he once was also a developer we thought can be trusted. So pardon me that I get suspicious when a teamless developer announces/starts work on a second game now.