Most van companies offer a "chassis cab" option [1] - basically a van with the cab present, but most of the back missing.
There's then an ecosystem of companies that will work with end users to design, build and fit custom van bodies. If you want a mobile broadcast van, or an ambulance or a mobile command centre? That's where they come from.
If you see delivery vans that aren't standard models, they've almost certainly come through the same ecosystem; companies like VW generally aren't in the business of working with end users on custom products.
Deutsche Post uses a fair amount of the standard "van-type" vans by VW, and even if someone else is making a custom body electrifying the chassis is clearly a job for VW.
Given that VW's CEO has been whining to the press about how annoying it is that VW is now not their customer but a competitor, they clearly now think that they should have wanted the job more. My guess is that they did not expect the Post (which as a massive, formerly state-owned company you'd expect to be fairly conservative) to risk going their own way and succeed with it, and thus misjudged the risk involved with letting them pass.
There's then an ecosystem of companies that will work with end users to design, build and fit custom van bodies. If you want a mobile broadcast van, or an ambulance or a mobile command centre? That's where they come from.
If you see delivery vans that aren't standard models, they've almost certainly come through the same ecosystem; companies like VW generally aren't in the business of working with end users on custom products.
[1] https://www.google.com/search?q=van+cab+chassis&tbm=isch