We know that PCs have a cap of 20.
NPCs can have rolled stats.
An NPC can break the rules have stats high or lower than the normal. An Orc NPC can have 22 STR before getting to level 20.
There is an NPC ogre out there with STR higher than 19. And with them being large, this strong ogre can lift almost a ton. That's super strength.
This isn't a coherent argument. This is a bunch of random statements barely strung together.
Yes, we know that PCs have a cap of 20... that has nothing to do with saying an elite human caps at 19, in fact, it disproves that unless you don't think that PCs can be elites. It is just a random statement with no bearing on the conversation.
NPCs can have rolled stats? Okay... sure? I could decide to roll stats for a cat, but I don't need to. I usually don't in fact. But just because you CAN roll stats for NPCs doesn't mean that you logically must, or that your method for determining modifiers makes any sense.
For example, using your method, I can determine that humans have the following modifiers
#1 -> +4 wisdom, +1 charisma
#2 -> +4 dex, +2 con, +10 int, +5 wis, +6 cha
#3 -> +1 str, +6 dex, +4 con, +3 int, +1 wis,
#4 -> +6 str, +2 dex, +7 con, -1 int, +1 wis, -1 cha
#5 -> +0 to all
These are all real modifiers that I would get from real human statblocks. So, again, your method is unsupported and leads to bizarre, unsupported results.
Can NPCs break the rules? Yes, of course, that doesn't mean anything. Can there be an NPC ogre with more than 19 strength? Sure. But you can't declare confidently that the rules support an ogre with a strength of 27. They don't, anymore than they support an NPC human with an intelligence of 28 or a strength of 24
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But, going back from dealing with all of that
But the real point here was to remind you and others that "human" limits are a bit squishy in DnD. Most martials end up as strong or stronger than ogres, Barbarians can end up matching dragons and giants with ease. But also, these are the exact same limits faced by elves, dwarves, warforged, goliaths and goblins.
We said it earlier, when running for days to run down the orcs, Gimli, Legolas, and the Orcs could all keep that pace because.... they were orcs, elves and dwarves, it was just expected of them. But Aragorn needed to have special lineage powers and training. Well, in DnD... elves, dwarves and humans are all on a level playing field. So using "human limits" doesn't make immediate sense.
Again, this was the point I was getting at originally. When I asked where my warforged landed on your chart, when I pointed out that humans can be stronger than ogres, I wasn't trying to get into a discussion on the limits of NPC creation, but to instead point out that not all PCs are human, and earthling limitations in DnD aren't something that make a whole lot of sense.