Well, 1.0 means you have one of something. Whether it be a pizza, or a game/program. I don't think any studio actually managed 0.9 version actually meant 9/10s of the game/program. Some instead used it to track progress between milestones. If one had 10 milestones, they would do the tenths (0.10, 0.20, 0.30, etc) for milestones, regardlesss on how much data each milestone actually required.
With the popularity of EA though, this kinda went out the window. Just like the progress bar of old that actually meant something, to be replaced with a bar that filled, and emptied 100,000,000,000,000,000,000 times, to now something just as meaningless, a spinning circle. I know it's going to happen because I'm mentioning it, but I'm currently surprised they haven't borked DL progress bars yet.
Oh well.
Now that I've finally finished paying off my car, I may visit you over by Patreon. Because I'm going to have to cast my vote for Elsa, Mia, and Sophie... or maybe the Church sisters... we'll see.