Hmmmm...... can't say I agree with this method. You'll basically train your head to be "comfortable" going slower. I'll have the hairs on the back of my neck stand when I make a turn faster or find a new braking point. It isn't a "oh shit" moment, but basically my body saying "I've done this before, but not this fast!". But the next time I do it, I won't get that rush again, body/brain get used to it.
And from a technical point of view: practice/trackdays should be used for tuning suspension at the very least, not just 'learning lines'. Your suspension will react very differently going 20-30 km/h slower or faster. If you're set for your "slow pace", It's likely you'll run into problems when you get to your BWAHHHHH pace.
And on a personal note: where's the fun in that?
Well, I'm not talking about poking around the whole track in 2nd gear or anything. There's a definite bell curve to my pace over the course of a track day though. First session usually has a slow sighting lap, so you only end up with 2-3 hot laps, and the brain and body is warming up. Session or two after that I'm starting to get in the groove and probably 3-4 seconds off my previous pace. Next 2-3 session in the middle of the day I'll try to really push, and (hopefully) pick up a few seconds from my last outting. Then the last session or two I'm usually starting to run out of steam and I'll back off a little and work on body position, or just being smoother, etc.
Progress has been slow though, so maybe I need to go out there and just start bombing it from the get go.
The times that I do that though, I'll either start making a ton of mistakes, or I'll go way faster, and have no idea why. There's one specific time I can think of where I dropped like 3 seconds following a control rider, but I have no idea what I did different and couldn't repeat it, I was just so totally focused on staying pinned as close to the back of him as I could. He also said something dickish when we were talking before we went out like "Yeah, well maybe this just isn't for you" and I was absolutely determined to stay right on his ass.
Or they turn too tight, especially on the exit in fear of going wide and hitting the grass. That was my biggest mistake I corrected this season. Just don't look at the grass :P
I tend to have the opposite problem, where I'm frequently trying to turn in too late. I think it comes from riding almost 10 years on the street, where out in the canyons I'm hesitant to to commit to a turn until I can see all the way through it - so if a corner is blind at all, I end up waiting way too long. I've gotten a lot better about it though.