Thanks for doing this. I hope it encourages more participation.
The capabilities of a triager mostly look good except for "closing PRs and issues". This is a superpower that has traditionally been reserved for more senior developers because it grants the ability to shut-down the work of another aspiring contributor. Marking someone else's suggestion as rejected is the most perilous and least fun aspect of core development. Submitters tend to expect their idea won't be rejected without a good deal of thought and expert consideration. Our bar for becoming a triager is somewhat low, so I don't think it makes sense to give the authority to reject a PR or close an issue.
ISTM the primary value of having triager is to tag issues appropriately, summon the appropriate experts, and make a first pass at review and/or improvements.
FWIW, the definition of the word triage is "in medical use: the assignment of degrees of urgency to wounds or illnesses to decide the order of treatment of a large number of patients or casualties." That doesn't imply making a final disposition.
Put another way, the only remaining distinction between a "triager" and a "core developer" is the ability to push the "commit" button. In a way, that is the least interesting part of the process and is often a foregone conclusion by the time it happens.