There are times when activation is necessary like when you get the urge to check some code or look at the book. It's the inner miind helping to make the information conscious so it never hurts to follow that and activate. If you're ignoring that curiosity I'd say that is more of a roadblocks to the success of Direct Learning since the conscious mind does seem to need to make certain connections before we move on.
How proficient we become I suspect remains based on a "need to know" basis. If it isn't that important to us or we only use the skill occasionally then the results will be difficult to see. Like if you photoread a book on developing your skills as an artist and spend the weekend painting... feeling in the flow and your work has developed into a nice style and is not quite there yet, but it's only a hobby and you set it aside for some months then it wouldn't surprise me if you fall somewhat short on your experience of that weekend when you try again. I say somewhat short because I believe that once you had an experience that experience you cannot fall back to the full state of the unlearned. You will always know something from the experience even if you cannot quite reproduce it at this time.
If you continue to use the skill regularly every other day or so I think you'll look back a few months later and notice that at some point your work took a real turn (or someone else notices for you and that seems to happen more often than not). I think the reason we don't always see the DL in progress is because we're not comparing ourselves with the book, "am I doin't this right? Haven't quite mastered that yet." Thought's along those lines don't exist because we a sort of flowing into it and learning again like we did as small children. Our ignorance at that time only knew if others can do it I can too so I just keep imiating it till I get it. There were errors along the way but we didn't stop to say why can't I do it? I followed all the instructions. Our instructions were our own 'testing' so we learnt to walk rather quickly when we found our muscle. I see the same sort of process with DL our minds probably test out the theory and because we don't consciously know the theory we just flow with testing out little modifications until it seems to work for us.
Sorry I seem to be rambling... in a writing mode I guess. 
Alex
