By definition, anything I say is my opinion. As for whether it's "factual," I'm not sure how you judge that. There is only one factual authority for determining whether something is part of the rules as written, and that's the rulebook. Changing what the rulebook says is a house rule.I assume you mean this to be your opinion and not something factual?
Now, there's nothing wrong with house rules! And I totally support encouraging players to propose customizations to their spells and abilities. But it is just as much a house rule to say "My magic missile looks like arrows shot from a bow" as it is to say "My magic missile does 1d6 damage instead of 1d4+1." Either one is a customization that I would be okay with, but they both change how the spell works in play. For example, now a wizard can kill people by magic while pretending to be a magic-less archer. In some campaigns, this won't matter, but in others--say, a campaign that takes place in Dragonlance's Solamnia--it could matter quite a lot.
Or suppose I say, "My magic missile looks like a balor that appears, roars, and slashes the target with its claws before vanishing in a cloud of smoke and flame." At this point, what we've got is no longer an attack spell with flashy visuals; it's a multi-sensory illusion spell with no saving throw, that happens to deal damage! A clever wizard with a decent Charisma can use this to terrorize all manner of foes. You may still be okay with it, but it is a big power boost for a 1st-level spell, even though none of the numbers have changed.