There is currently an effort underway to improve the bound. They have reached at a much larger kappa around 0.001635527380375392
That unintentional mockery of a repo is 262million lines of such moves and growing. I don’t think for a second anyone involved has a clue about complexity theory though or they’d just jump to the obvious “O(1) time complexity using an O(2^n) lookup table to cover all possible n bits of input” which is the final end state of Blums speedup theorem.