Oregon's Mandatory Reporter list is similar to Alaska's, but not as broad...
Alaska's applies to anyone employed by a school district or institution of higher education¹, anyone employed by a law enforcement agency or holding a law enforcement credential, anyone employed in a medical or psychological business/agency, anyone holding a counseling or medical licensure, anyone involved in child care. (At least per the Anchorage School District's annual training.)
For educators, the mandatory report for anything in scope of work is not direct to OCS, but through one's school principal². Encountered outside of work, or off-hours and life threatening, it may be sent direct to OCS. And it applies even to the janitorial staff. If one counts as a mandatory reporter, saw clear indications of abuse, and are shown to have thought it should be reported can be charged with failure to report.
I will note also: in Oregon, Linn-Benton Community College has in their student trainings a strong encouragement to report suspected abuse/neglect of children
and elders, and spousal abuse.
Given mentions of the PPB, Greylond being in Oregon, and being warned that he was obligated to report it implies something about Greylond.
Yeah. That is not even a little bit how mandatory reporting laws work, and they sure as hell don't apply to random strangers in gaming stores.
For those who are mandatory reporters, yes, it really is. If you even have to ask "is this abuse?" you report it. Greylond's initial concern was sufficient for a mandatory reporter to have been obligated. We do not have clear statement that Greylond does or does not have mandatory reporter status.
The operative phrase in what you quote is "reasonable cause". Let me put emphasis on reasonable.
"I saw the parent shout at their kids once," really does not count as a reasonable basis to suspect overall abuse. It is not a reasonable leap - it is at best a leap of intuition or fear - as is atested by how many folks here said so early in the thread.
The threat of expulsion from the household pre age 18 is very much a mandatory report act. It's explicitly so in Alaska.
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¹: college, university, or career training agency or business.
²: in writing. Keep a copy. The principal can decide not to advance it to OCS. Scope of work reports filed directly are grounds for termination, especially if later shown to be unfounded.