Good eye! Glue would be my guess.
The person who did this work currently has an ambitious project adding two "tiny homes" to their rural homestead. I offered to share my insights only to be flatly rejected. Can't have that -- we know you're a pro and will be far too fussy. We just want the bare minimum, just a few plugs. No need for more than an extension cord from the trailer pedestal to each "home."
This is in the same area where a business ran power to their sign by laying the conduit (EMT) in a shallow groove they had cut in their parking lot. No need for minimum depth if it's "not buried." Over the decade since that conduit has been broken countless times. The guy has tried laying angle iron over it, placing parking blocks along it . . . everything except doing it right.
You can't fix deliberate ignorance.
