Actually "fixed" reference points are used by mostly all trainers in tarmac or dirt riding for any level of rider. Most schools/classes will set cones up on the outside and inside of the track, which are used as reference points.
The reason why using a faster guys reference points work is to push the rider. You start by simply riding the track slow, hitting those marks. It feels horrible because the line through most corners will be straight and you'll be going slow. Eventually you start to pickup speed and you start to form the "arc".
If you practice the right lines, the "fast" lines, even if you're going slow, you will memorize them very quickly. Knowledge is power and without that, by the rider simply making their own "slow" lines, it's nearly impossible to shift those slower lines to "quicker" lines. The rider will be stuck using those slower lines forever, unless someone points out the fast lines.
Skipping the years of riding slow lines and immediately learning the quicker lines (not talking Marc Marquez line's, just someone who has a decent pace) will dramatically increase your speed on the track. This is how MOST schools teach you how to ride. There are no "slow" lines or reference points, everyone uses the same "PROPER" line AND the "correct" reference points.
I guess you can take the slow road like I did and spend a year figuring out what someone could have told you in a 5 minute conversation.
Reference points are always fixed for a particular rider and speed...that's why they are called reference points. But there certainly is no "correct" reference point that is the same for everyone. If you want to square off a corner, you certainly use a different reference point for turn in than you would for a sweeping line. And reference points simply change if your capabilities change (speed, lean angle, approach etc.).
And if you want to push yourself, you move your own reference points...e.g. brake 10 feet later while using the same speed and the same line through the corner (if your exercise is to break harder). Taking your words, you could simply try Marquez's reference points next time in order to push yourself to Marquez's level....let me know how that works out for you.
And no, just because you are riding at a lesser pace, you don't have to learn what you call slower lines (whatever that is). Most people refer to the race line as being the "correct" line through a specific corner, but if you are riding at a slower pace, you simply cannot use the race line to its full potential....and forcing people to use it isn't beneficial at all. Perfect example is corner exit...the race line usually brings you out to the opposite side of the track, however, if you are not carrying the corner speed yet, you simply will not get to the opposite side - unless you physically steer to get there...and that is exactly the wrong thing to do. As your speed increases, the bike will automatically drift further towards the outside.
And I actually encourage people to try different lines through a corner, especially if they look into racing. You would be surprised how many people you can easily overtake by simply using the tighter inside line...especially those people who are die-hard race lines fans. There are many schools who focus only on the race line but with anything in life, it is not black or white...or otherwise everybody in MotoGP would be able to ride like Marquez...all they have to do is to use his "correct" reference points...right?
Anyway, I am not planning to get into endless discussions over this, I simply pointed out that the advice given needs to be treated carefully...and I provided the explanation as to why...