It's a daunting question. Yes, if government officials see a vulnerability in a system, they should notify the creator or the vendor of the system of the vulnerability as a principle generally applicable and implemented, yes. That said, encryption is a challenge to law enforcement, so I think I make a distinction between laws dictating the creation of back doors and laws that authorize the police to circumvent encryption through existing vulnerabilities for a certain period, because that may be the only way to actually perform the investigation.
I don't know, frankly, what the best solution is in this regard. I agree with you that there's an obligation to inform the vendor or the creator at some point, but how do the police...? I see what's being done here as less problematic than laws creating back doors, particularly where there's judicial oversight of the system.