Ive never seen anyone achieve those numbers legitimately through normal vanilla play, every screenshot ive seen with E tier numbers involve a mod that calculates all possible moves picking the mathematically best one probably also cherry picking a favorable seed.
A calculator is not a mod. But yes, the calculator is just doing what the player could do but faster. It isn't needed, just saves time. A good seed can also just happen, you don't need to use an optimized seed finder to find it, just play alot and get lucky. Either one, however, is not a mod. Even using those would not be considered playing with mods on. Mods are things that actually modify game files, which is what mod is the short form of.
Okay, replace "mod" with "third party tool" then. The point is, using a calculator removes a lot of human skill and cognitive calculation that contributes to fallibility.
You could make similar arguments about using programs to calculate optimal chess moves and how its "just doing what's human could do". We all know theres a difference. A human can't exhaustively compute billions of possible moves to find the best one the way a calculator does. Even card counters with photographic memory are prone to making suboptimal plays. Is it theoretically possible for a human to play mathematically perfect hands the whole run without tool assistance? Yes. Is it likely? Not really.
I personally don't see those numbers as legitimately achieved through pure human skill and cognition when you use a computer to brute force it and fish for lucky seeds.
The moment someone achieves those numbers on a random run without a calculator I will be very impressed.