When clicking "respec" on the GUI, you don't get 100% of your points back. That's great because it deters cheating the system, but it should have a tooltip when you hover over the button warning you, "You only get X% of your points back." or something similar.

Never mind, I hadn't tested it myself, and I was curious to see what your formula for loss was, and saw this is already a thing.

Just a typical case of a user not reading text.