But Harrison's Deckard isn't meant to embody that "ethics/work inspector" as a good actor would.

He is meant to portray him as a detective who is not that good with pretending to be someone else would.

Harrison might or might not be a good actor, but Deckard certainly isn't supposed to be a good one.

It’s just about the only comic relief in the film. Possibly it’s acted that way deliberately.