Business analysts can serve an important role helping the product owner elicit requirements and write user stories. I have not encountered someone who is technically the product owner who can do this on their own, usually they are setting requirements at the epic and feature level. There are even some small systems where a developer isn’t needed, the business analyst can use an interface to make changes. There is no one single scrum team composition, anyone who thinks there is has very narrow experience with the application of Agile.
Project managers can serve as the scrum master or product owner. In many cases the project involves quite a bit more than what a scrum team would do, especially when that scrum team is focused on a single platform or system. A developer on a scrum team is not going to coordinate training, compensation changes, procedure updates, telephony changes, communications, UAT, office space changes or anything else that can be part of a project. People who think that a scrum team can run a project are just usually not referring to something that is actually a project, a common problem at the bank.