0.71b iirc was implemented a couple of years back and it stayed that way with icstor continuing to milk supporters with out providing any updates. A bunch of people reported him for it (rightfully so - false advertising and all that). So Patreon investigated Icstor, and the game, told him to make a whole laundry list of revisions. Ending up with the 1.0 "final" update. Which, ironically, has been updated a couple of times the past week. Hence the "b,c, and d" updates.
They are, funnily enough, going to be releasing a series of DLC to add certain things and, potentially, cut content back into the game - Make that what you will.
Though that is yet to be seen as Icstor is, seemingly, desperate to want to crack on with his next game. Which makes sense. He has incredible poor form on ending his games. Almost as if he gets bored of it and wants to move on.