These kinds of things are always tricky, and always easier to see in hindsight. Everything is a trade-off.
I can easily picture a scenario where there is pressure to reduce time to release signature updates, and someone looked at a process where there was early testing (that would have caught this) and said "Over the past 5 years, we've deployed hundreds of signatures with exactly zero failures; why are we still doing this process that adds a pointless delay?"
I can easily picture a scenario where there is pressure to reduce time to release signature updates, and someone looked at a process where there was early testing (that would have caught this) and said "Over the past 5 years, we've deployed hundreds of signatures with exactly zero failures; why are we still doing this process that adds a pointless delay?"