No it doesn't. I didn't say anything at all about the DMG, let alone assume that anyone reads it. I pointed out that, since at least the late 1970s, there have been competing ideas as to what makes for a good GM, even in the context of GMing D&D. There is no single thing that is "good GMing".Well, that kind of assumes anyone ever reads the DMG for any version of D&D.
What will shape the experience is the procedures actually used in play. D&D has quite a long tradition of relying on procedures that are not actually written down in the rulebooks - the only two versions of D&D that come close to writing down all the intended/envisaged procedures are Moldvay Basic and 4e D&D.Certainly different games will give you a different overall experience
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The rules can only shape the experience in general.
But in any event, this is not really relevant to what I said in the post you quoted. What I said is that I am 100% confident that system can help GMing. By "system" I mean procedures of play - that is, how it is worked out who says what in the course of RPG play. For instance, if I as GM want to follow my players' leads in framing adversity and establishing consequences, then I want procedures of play that facilitate that. Moldvay Basic doesn't really spell out any such procedures - to the contrary, its procedures are focused overwhelmingly on establishing adversity and framing by reference to the GM's pre-prepared dungeon map and key. 4e D&D, on the other hand, does spell out some such procedures. Torchbearer 2e spells out more of them, and more clearly.