Rubber stamping is a separate issue. If that's what people were worried about, why would it be this case in particular getting everyones hackles raised? Every warrant to search a house or a car should be questioned, but this case isn't special.
They do need a warrant for any information to not get laughed out a US court though. This is the main reason they are going after the data this way, because they want what they found and know wouldn't survive discovery to eventually be admissible as legally obtained evidence. That and it will set a nice precedent for them to deputize private persons and corporation into being law enforcement when they just can't be asked to not fuck up one simple thing.
This is also not-coincidently a case likely to polarize people against Apple with the old faithful terrorists are coming to get you rhetoric. A most slippery slope indeed, nearly guaranteeing that everyone who is supposed to be checking the executive branch for overreach will just go along with them wholesale.
That doesn't prevent them from acting upon information received from Apple outside of the court system.
There is a reason parallel construction is a thing.