I'll object to that. To my eye, the whole "flavor text vs. rule text" is both recent and unwelcome. In Classic D&D the whole work was just "rules". There may have been parts easier to change and parts harder to change, but there was no "fence" between them, and any description had potential side-effects you could use to your immediate advantage in-game.
When did I say anything about flavor Vrs rules? My point was that flavor has alwyas been easier to change then the rules, and that it's always had elements of flavor not called out rules wise. If you want them to have an effect, that's perfectly valid, but nothing is actually mentioend in the rules.
What do the rules say about how easy it is to spot a magic missile? Can you see by a magic missile?
What about entropic shield?
What if I color my armor white? Or Green? Or If I paint a big eye on my shield?
Do the rules have an issue with me making a magic speaking tube instead of a mouth? Or instead of a mouth making it look like a parrot? What if I just want it to look like an orc mouth instead of a human mouth because I'm an orc casting a spell? If I make any of those changes will it effect what the spell does?
What if instead of a bit of wool and a piece of metal I use a pickle and a copper wire? I'm still using components, what difefrence does the actual object make?
What if I just go generic and say: "I use my components to cast the spell." Do the rules break down?
If I write my scrolls in blue ink instead of black do I still get my loan? err wait...
None of these things have any kind of specific effect called out in the rules. If you want to make them have an effect in your game, cool, you have every right to do so, but changing them doesn't have any effect on the rules in the book.
The original rules used 1d6 for every weapon and all other aspects were just flavor. Oh you use a sword instead of a dagger? d6 damage! An axe? cool it does d6 damage!
I don't believe there's a new "fence" being made... I think it's just a case of people paying attention to how flavor and rules interact, and using that to the game's advantage.