Propylene glycol is simply a cosolvent (e.g., benzyl benzoate, ethyl oleate, and guaiacol); it doesn't have much effect on the PK of the drug.
GLP-RAs have a very short half-life in the body (approx 2 minutes), so pharma chemists either modify the structures with covalently-bound moieties (e.g., fatty acids, human serum albumin, or a portion of an antibody called the "fragment crystallizable" region), change the amino acid sequence of the protein, or alter the delivery matrix with a micelle-forming polymer like PLGA.
The modification that is used for semaglutide to produce Ozempic is the attachment of a fatty acid to the protein, increasing its half-life significantly. This is why it is dosed once per week.
If QSC's semaglutide does not have this modification and is just the unmodified protein, then the half-life is incredibly short, which would help explain the lowered efficacy.