You should of got the 4 bolt slipfitter version as this was a custom-ish order. Well not exactly custom since you bought it with the specs pre-done from graybar, but you got it from them as a special order, you ordered one and then Graybar ordered what you told them to order directly from AEL then AEL made it for you. xD So it's kind of custom.
Linemen prefer 2 bolt setups. Makes for a quick install. The company likes more lights fixed during the day since we are trying to save our streetlight business since towns are now buying them out and maintaining them themselves. We have already lost 5 of our 59 towns in western mass.