PO interacts enough with the Developers
Is the Sprint Review the right place to determine if the Product Owner is interacting enough with the Developers during a Sprint or observe whether the Product Owner has provided enough information at the Sprint Planning to make his presence optional during the Sprint?
It sounds a bit late to me. Commitments were made and now the Sprint is drawing to a close.
The purpose of the Sprint Review is to evaluate the work that has been Done and which remains to be Done, so the Product Backlog can be updated. If the team have failed to collaborate in a timely way so commitments are met, there's a formal opportunity in the Sprint Retrospective to make actionable improvements.
No.
The purpose of the Sprint Review is to inspect the outcome of the Sprint and determine future adaptations. The Scrum Team presents the results of their work to key stakeholders and progress toward the Product Goal is discussed.
Sprint Retrospective is an Event purpose built for the Scrum Team to discuss what is working and what is not.
The purpose of the Sprint Retrospective is to plan ways to increase quality and effectiveness.
The Scrum Team inspects how the last Sprint went with regards to individuals, interactions, processes, tools, and their Definition of Done.
Daily Scrum would also be an Event where Developers could raise a need for PO support and clarity.
Daily Scrums improve communications, identify impediments, promote quick decision-making
Team can also raise any issues they have as they are having them, rather than saving it up for a particular event.
Product Owner is a member of the Scrum Team and presence shouldn't be considered optional. PO can delegate some responsibility for activities to others on the Scrum Team, but they always remain accountable.
Are you asking this specific question as a result of something you are currently experiencing?
The Sprint Review is a place to see the results of the interactions between the Product Owner and the Developers, but it's too late to see the effects of the interactions and make changes. The Sprint Review is a good opportunity to see what kind of feedback the key stakeholders are providing and understand the value those stakeholders are getting from the Scrum Team. If the team is not achieving goals, achieved goals don't line up with stakeholder needs, or the team is struggling to understand the work, that could point to some problems with interactions between the Product Owner and Developers.
For earlier insights, I'd look to the Daily Scrum. Although the Daily Scrum is for the Developers, this is an opportunity for the Developers to plan their day. If they discover that they need insights from the Product Owner to better understand the work or make decisions on what the next steps should be to maximize value, they should get it. Otherwise, an inability to talk to or get information from the Product Owner becomes an impediment.
The Sprint Retrospective is the right venue for the Product Owner and Developers to talk about how they are interacting and ensure that their ways of interacting are working and helping the team to be successful. If there are any changes to be made, this is the place to think about what those changes should be and how to enact them.
I don't think that a Product Owner's presence can ever be optional in a Sprint. Scrum - and agile methods in general - are best suited for cases where the work is not predictable and unknowns emerge by doing the work. In fact, the Manifesto for Agile Software Development makes it clear that "business people and developers must work together daily throughout the project".