No it isn't. They're buying 2-day shipping from UPS or FedEx, both these companies make a "best effort" to deliver the package within 2 business days. That's not always possible without greater expenditure than the companies consider 'reasonable' (and their terms speak to), that's why there are guaranteed next-day and 2-day air freight options from both.
The complaints are generally not about UPS or FedEx. They are about when Amazon thinks the shipping distance is close enough that they can use any service at all to meet the 2-day goal, but the services end up being terrible and unprofessional. Like LazerShip which is just a dude with a car.
If their "2-day shipping" service doesn't result in the package being delivered within 2 business days a vast majority of the time, they shouldn't be advertising it as "2-day shipping".
