The Short Version
Apple released firmware build 8B40 for AirPods Pro 3, the first update since version 8B39 last month, with no release notes published yet.
AirPods Pro 3 got a firmware update, version 8B40, and Apple said nothing about what changed. AirPods Pro 2 and Max 2 were skipped entirely. The update likely fixes small bugs, the kind you never notice. Owners of older models are simply left waiting.