It's basically how Itch.io works.
Information on how updated content and donations works in regards to updated content is pretty damn vague on Itch.io.
We didn't want to make a new project page just for the updated pricing so we decided to go ahead and take the loss in regards to those that paid for it before the early access stage.
Sure the money would have been extremely useful in getting Uni finished, but at the end of the day we're making a game to entertain our players. Not a lifeless product to churn out and chase the next big thing.
At the end of the day as long as our players have fun and enjoy our game that's all that matters to us.