Good points, but to me, this is not a pure OFPF system. It's been modified to fit a BG with a 34" scale length, by allowing this "wiggle". That's fine. But it is not the exact same OFPF system people used on a 25" 6 string guitar, because there, there is no "wiggle". There, a player can trill an F and Ab on the E strings 1-4, or octave Ab's 4-1, without an audible wiggle.
I would say that in reality, there's no such thing as a "pure" OFPF system, in the sense you seem to mean. There is no system that mandates one finger and only one finger per fret.
I would go farther and say that in a sense, there is not even a OFPF "system" at all. There's no fingering police. The point of working on OFPF is to develop your capacity for using all of your fingers, and doing so over a reasonable stretch. Not to stretch your fingering system on some Procrustean bed of conformity.
This is a commonly misunderstood point, and I wish it were better understood.
If you want to talk about guitar fingering, I've been playing guitar for 40 years and I can tell you that in classical guitar at least, although you are taught to hold your hand in such a way as to enable you to do OFPF, and you are taught common scale fingerings that make use of that type of fingering, this is for training and exercise as much as actual use. There is no mandate saying that when it comes to playing actual music, you have to use 1-3 when you go from, say fret 2 to fret 4. It just is not that rigid. technique is only a means for achieving a result. If the situation suggests that you're better off using 1-4 for that, or even 1-2, then that's what you do.
The thing about learning OFPF is that it's difficult to use something you haven't practiced. When you focus solely on 1-2-4 in lower positions, you are making yourself NOT use the 3. Should you then want to use the 3 in that setting, it's likely to be harder for you to do so ... because you haven't practiced it. You may be able to get by perfectly well without it, but it remains a fact that you are not practicing the use of the 3 in the lower positions.
OTOH, it's easier to NOT do something you do know how to do than it is to do something you don't know how to do. That is, many of us think it is better to have a capability you don't always use than to lack a capability you may occasionally want to have. Hence OFPF. If you can easily use your 3 everywhere, you can decide when not to use it. But if you haven't developed your 3 as much, you have less capability to decide when and where to use it; you will be limited
to some extent by your relative lack of practice with it.
Again, and I can't stress this enough, OFPF is not some rigid system that mandates you do finger stretches in one and only one way. That's a fundamental misunderstanding IMO. Rather, it is a means of inculcating the capability to use of all of your fingers on all parts of the neck, as you consider necessary. Again, you can't effectively use what you don't practice.
None of this, in any way, means that OFPF is obligatory or that you can't be any good if you don't use it. It does mean that there's a point to it, and that it's not what folks sometimes think it is.
