Not sure where you are getting that info, but even with the pay freeze I make about $20k more now than I did in 2008 due to the pay for performance plan.
Without a yearly COLA the money that was allocated to step increases was still there. The very first year of NSPS had a rather large COLA so if you did well under NSPS you got a huge raise. The following years were much more moderate, this last year there was a small COLA and the raises were pretty decent.
You can get a 5 and not get a raise if you are at the top of your pay band. At that point all the money goes into a bonus.
Unfortunately "bonus" became an ugly word last year due to some agencies paying rather large bonuses to GS employees.
That freeze was lifted, but bonuses under NSPS were capped at something like 2%
So, were at the top of you pay band and each year got a significant payout, you did not get a raise, your base pay stayed the same.