It always felt like, IMO, that we end up testing it ourselves anyways. Obviously we don't go through the whole spec, but like you, we implement what we need and find the relevant bugs/errata ourselves. It's very painful to run across these and I don't recall an MCU that doesn't have at least one that we run into and have to workaround because development is already deep enough that we're economically locked it and it wouldn't be worth the rework to switch to a different MCU. Sometimes the bugs are in the silicon, sometimes they're in the middleware, but both are very painful to root-cause.
It always felt like, IMO, that we end up testing it ourselves anyways. Obviously we don't go through the whole spec, but like you, we implement what we need and find the relevant bugs/errata ourselves. It's very painful to run across these and I don't recall an MCU that doesn't have at least one that we run into and have to workaround because development is already deep enough that we're economically locked it and it wouldn't be worth the rework to switch to a different MCU. Sometimes the bugs are in the silicon, sometimes they're in the middleware, but both are very painful to root-cause.