I am 99% sure that the bonus won't apply for my planet until I actually enter the planet and hover over the resource the planet is gathering. I am using Google Chrome as browser. It's like the game won't know the planet went from xx% to (xx%+20%). I will try and take some screenshots later today way after the time I reckon one of my last planets should level up development.

Yup, you gotta go back and check on them to make sure theyre up to date. Think if it as your managers realizing that productivity is increasing but your not noticing so there taking it for themselves so until you go in and check to see how much your actually making they're able tot take some of it

Is it a bug ? Or a feature ? If it's a feature then maybe a timer would be useful. Or not. On the other hand I'm glad I'm not imagining things.