If the initial first parse of a layer's conf/layer.conf (to get the dependencies) fails, we aren't logging anything in the update log. For example, a layer recently added to the layer index was not adding to BBFILE_COLLECTIONS in layer.conf; there was no UI-visible update recorded against the layer containing this error in it thus it was not possible to see that this was the problem without running the update manually on the server side with debug logging enabled.
Still valid. The first pass is only observable when running on the instance/container.