What a receptor-binding paper is actually reporting
A receptor-binding paper reports how tightly a ligand occupies a named receptor in a defined assay, which is not a statement about human use.
Incretin papers, and a lot of peptide pharmacology beside them, include a binding or functional assay. A cell line or a membrane preparation expresses one receptor. A labelled reference ligand, or a second-messenger readout, sits in the well. The test peptide is compared with that reference. The published figure is an affinity or potency value for that system, often an IC50, a Ki, or an EC50, and sometimes a panel across receptors when the authors argue selectivity.
Those numbers belong to the assay that produced them. A different cell line, a shift from binding to a signalling readout, or a different salt form can move the result. Authors use the panel to say a molecule prefers one receptor over another in the systems they ran. The figure is not a schedule, and it is not, by itself, evidence of an outcome in a person.
When a note on this site says a catalog compound is "described as" an agonist at a receptor, the sentence is pointing at this kind of paper. The certificate of analysis still has to show that the vial matches the sequence the paper studied. GLP-3R, Terz, and Sema are the listings that lean on this literature most directly.