The USPS is an US federal agency. At one time it even had a cabinet level position though not so any more. Its not private like in most countries. At the scale they buy these vehicles, it probably makes sense to get a custom one. Even Amazon has custom EVs built for them.
Eh, sort of. Amazon partnered with Rivian to help design the EDV and had an initial exclusivity agreement as long as they ordered a certain number of them, but this agreement has since been terminated so anyone can buy them now. The USPS actually tested one in early 2024.
Its not clear what your point is? Both USPS and Amazon got heavily customized vehicles made for them. In the US the USPS is a government agency so any kind of government contracts get heavily securitized by the public but nobody cares what trucks Fedex and Amazon buy just like in countries where the mail service is privatized.
IMO a LLV or NGDV is a custom-designed vehicle for USPS, the EDV is a delivery-optimized electric step van that happens to have been designed with the input of one specific delivery vendor.
