The Change Optics Report is documented as a pre-enablement planning tool — a sample set to help tenants prepare before enabling RejectDirectSend. Our situation is the inverse: the setting is already enforcing in our tenant, legitimate business mail is being rejected, and the rejections do not appear in Message Trace or Extended Message Trace. Confirmed by Microsoft support case.
That leaves no way to determine what is currently being lost. A sampled report with roughly 18 hours of retention cannot serve as an incident inventory, and the guidance to use Message Trace for further detail doesn't apply, since these messages are rejected at the edge before acceptance.
Two requests: full rather than sampled DRS data, and retention matching the date range selector. In our tenant this scenario is generating hundreds of rejections per week across four distinct sending platforms, and users have no way of knowing what they are not receiving.