The spring on top in this photo came out of the F2 front end on my ‘88 CBR 600F1. Back then springs were long. Now days, springs are a lot shorter. I saved 300 grams in each fork by replacing the long springs with shorter springs of the same rate and longer spacers.
Yes, the rate increases the more you compress a spring but not by much. I think the advantage of less weight is greater than the problem caused by a slight rate increase near the end of the forks travel.