I really like this idea. The only problem with it is you have to adjucate between spell and not-spell on a case by case basis, which can be tedious.In-world I treat Spells as only things that arcane casters know, use and cast. Any other magic might be given the nomenclature of "spells" in the rulebooks for the ease of game clarification, but I don't consider them "Spells" in-game.
For instance... a High Elf's cantrip they get for free I just consider to be a magical effect they get for being highly magical creatures. It might have the name of an official "cantrip" in the rulebooks... but I find it kinda lame from a world-building perspective to consider that all High Elves have had to "learn" how to "cast one cantrip spell" (and that's all!) at one point in their lives... rather than just having some innate magical ability to do X. To me... they are magical, they can do X magical effect, and we only just USE the concept of cantrips and spells from the game rules perspective to make it easier for players to run and understand it as they play.
Likewise... the Path of the Totem Warrior can "cast" the beast sense and speak with animals "spells" but only as "rituals". But to me... thinking of them doing the exact same things that Wizards do is like really, really lame. That these barbarians "cast spells" just like Wizards. So I don't treat them like that at all. To me... these are both just natural abilities that barbarians have that produce the effects of what you would get from beast sense and speak with animals spells. But I don't see them as spells and don't treat them as spells. I basically treat them like their own individual class features that the rule book could have written out fully (like they do for other barbarian features like Rage or Unarmored Defense) but chose to just say "it's these two spells" because it saved space and explanation time in the rules.
And it's also the way I get around the whole "All Rangers are magical spellcasters" debate too. If having a Ranger that does not cast spells is important to someone... the easiest way to do it is just select those Ranger "spells" that can essentially be considered non-magical and treat their effects as if they were not spells and just Ranger class features. A Ranger can move an extra 10 feet a round? Sounds completely plausible. So let's just wipe away the fact that those 10 feet come from the Ranger "casting" the longstrider spell... and just say that this particular Ranger is particularly fast. Or that when the Ranger heals someone, they are using their knowledge of herbs and natural remedies to do so rather than "casting" cure wounds.
The Spells section is what it is just for ease-of-use. So I don't get hung up on it.
Oh well. I have a 300+ book of house rules, so tedious obviously isn't a problem for me!