Good question. I do know NYC issued SxS shotguns up through the late part of the 20th century.

Another:
Are pump & semi-auto guns with internal hammers drop safe?

Last:
Does it matter for a long gun?

We're talking a drop on the muzzle from some height for a "non-drop safe" shotgun. Most long guns, rotated to be perpendicular to the earth from a carry position, are "already there" in many cases. Meaning, there is mighty little drop or distance over which to accelerate relative to a hand gun.

This issue, while interesting, may not be significant for HD/SD shotguns.