The Developers on the Scrum Team share accountability for the Sprint Backlog, which is a forecast of the work and the plan to deliver the Sprint Goal12. The Sprint Backlog is dynamic and can be updated by the Developers as more is learned during the Sprint34. The Developers are not individually accountable for the items in the Sprint Backlog, nor are they assigned by the Scrum Master or the Product Owner5.

Explanation
It is true that the Sprint Backlog is a result of Sprint Planning, and it includes the Sprint Goal. This is because:
* Sprint Planning is an event where the Scrum Team plans for the upcoming Sprint. The purpose of Sprint Planning is to align the entire Scrum Team around a common goal and a plan for delivering an Increment that meets that goal.
* The Sprint Backlog is the set of Product Backlog items selected for the Sprint, plus a plan for delivering them as a "Done" Increment. The Sprint Backlog is owned by the Developers who use it to organize and manage their work during the Sprint.
* The Sprint Goal is a short-term objective that provides guidance and focus to the Scrum Team throughout the Sprint. It is a flexible and negotiable commitment that can be adjusted as more is learned throughout the Sprint.
* The Sprint Backlog is created by the collaborative work of the entire Scrum Team during Sprint Planning. The Product Owner proposes how the product could increase its value and utility in the current Sprint. The Developers discuss how they can deliver a "Done" Increment that meets this proposal. Together, they define a Sprint Goal that summarizes why the Sprint is valuable to stakeholders. Then, they select enough Product Backlog items from the top of the ordered Product Backlog to satisfy the Sprint Goal. Finally, they create a plan for how they will deliver those items as a
"Done" Increment.
References:
* [Scrum Guide], page 14, section "Sprint Planning"
* [Scrum Guide], page 15, section "Sprint Backlog"
* [Scrum Guide], page 15, section "Sprint Goal"

The Product Owner wants the Developers to adhere to its Definition of Done to have complete transparency into what has been done at the end of each Sprint. This is because:
* The Definition of Done is a formal description of the state of the Increment when it meets the quality measures required for the product. It is a shared understanding among the Scrum Team and the stakeholders of what "Done" means for any Product Backlog item that is selected for a Sprint.
* The Developers are accountable for creating a "Done" Increment in every Sprint. They must ensure that every Product Backlog item they work on meets the Definition of Done before it is considered complete.
* The Product Owner is accountable for maximizing the value of the product resulting from the work of the Scrum Team. They must inspect the Increment at the end of each Sprint and assess how it delivers value and contributes to the Product Goal.
* Having a clear and consistent Definition of Done helps the Product Owner have complete transparency into what has been done at the end of each Sprint. It also helps them make informed decisions about releasing, adapting, or continuing the product development.
Other options, such as predicting the team's productivity over time, knowing what the team will deliver over the next three Sprints, or reprimanding the team when they do not meet their velocity goal for the Sprint, are not valid reasons for wanting the Developers to adhere to its Definition of Done. They may reflect a misunderstanding of what a Definition of Done is or how Scrum works.
References:
* [Scrum Guide], page 10, section "Definition of Done"
* [Scrum Guide], page 7, section "Developers"
* [Scrum Guide], page 6, section "Product Owner"