From a design point of view, what limits the slate to 1000 pounds towing capacity

[AZFox]

That is a step bumper. Trailer ball bolts through hole in the horizontal surface below the license plate. Every truck I have owned has had a very similar bumper with holes in it to mount the trailer ball. It is only rated at 1000 pounds, the step bumper is good for it.

I've towed with a hitch ball mounted on a bumper since several decades ago, so I know how that works.

That's why I can look at the bumpers we've seen so far and tell they weren't designed to accept a hitch ball and safety chains.

Slate's design philosophy is to leave out what isn't necessary.
It's not necessary for the stock bumper to have towing capability.
Slate will offer a Hitch Receiver accessory for towing.

 

[KevinRS]

Slate's design philosophy is to leave out what isn't necessary.
It's not necessary for the stock bumper to have towing capability.
Slate will offer a Hitch Receiver accessory for towing.

Part of what is confusing on it is the standard bumper looks like a step bumper, which would have holes or knockouts for a hitch ball and for chains to hook, which would probably be the cheapest possible option, and fits with the stated tow rating.
Then the upgraded bumper is definitely not a step bumper, more of a box bumper, with the license plate right where a hitch might go, and a shallow sloped plastic underside with no frame or other metal visible where an accessory would mount.
It's got to be something that just wasn't designed yet when they built the prototypes we've seen, probably 5 or more months ago.

 

[AZFox]

Part of what is confusing on it is the standard bumper looks like a step bumper, which would have holes or knockouts for a hitch ball and for chains to hook, which would probably be the cheapest possible option, and fits with the stated tow rating.

It would be cost less to make it not capable and require the Hitch Receiver option if you want to tow.

I'm assuming a more capable bumper costs more to make, which is a pretty safe assumption.

 

[KevinRS]

It all depends on the decisions they made, and we probably won't know any more until they make another round of announcements, maybe in October when they start the tour back up.