Making progress simply means not dawdling or missing opportunities to go when traffic in front is slowing you down.
Some people incorrectly interpret that as riding as fast as it is safe to go in a national speed limit, regardless of the legality of it.
The official line is stick to the speed limits at all times, especially if you are on an observed ride or on a test.
The unofficial line is, you are a big boy make up your own mind. Most tend to stick to (most) posted limits and then whatever they consider to be safe in the NSL.
As a current Police class 1 advanced and pursuit driver, I'd tend to agree with this post, it does show the common sense approach. The only thing I'd like to add, if I may, is ALWAYS observe posted lower limits, without exception, and save progress for the NSL's, where the advice above I think is good.