> I don't know the pharmacokinetics of GLP-1 drugs but my guess is that they don't have the same sort of effects on SC tissue?

They do, but nothing like insulin does. GLP-1 drugs are more centrally and viscerally active than subcutaneously active, so the effects locally are more related to the physics of injecting solutions subcutaneously than the drugs themselves. They're also much smaller doses than are needed for insulin in general, so the volume averaged over a week is pretty tiny.

Also, as a result of the relative lack of local activity, injection sites are basically unlimited (anywhere from above the knee to above the elbow, except the neck) without fear of lipohypertrophy in the local area.