Accepted answer
96.8 per cent is at the top of what stepwise synthesis delivers on a chain this long, and it is reachable rather than fictional. Every coupling is high-yielding and none is quantitative, so the deletion and truncation sequences that survive purification are what occupies the remaining 3.2 per cent. Above roughly 98 per cent you are fighting the purification rather than the synthesis, which is why a 96.8 per cent figure on mazdutide deserves a method question — column, gradient, wavelength — rather than either belief or dismissal.
On the detail: gradient slope is the most powerful parameter and almost nobody mentions it, which is why two reports on the same material disagree by a point.
Sample solvent strength affects peak shape — if you inject in strong solvent on a gradient starting in weak solvent, the solvent peak can distort your main peak or create a false shoulder.
Concretely, buffer versus acid in the mobile phase changes the ionisation state of basic and acidic residues, shifting retention and selectivity — same vial, potentially different separation.
Published side-by-side method comparisons show that a two-point difference in purity on the same vial is easily explained by method choice alone.
Compare purity within a single laboratory on the same method, never across laboratories.