First is an assumption that the capabilities of the missile being tested are "known" and a follow on assumption that the PRK does not have the capability of flying a missile as far west as Burbank, CA.
Neither of these are very good assumptions to make. To understand why, consider the following;
KP's collaborates with both the Russian Federation and China on weapons development (multiple open sources) and both of those nations have missile technology that can go from anywhere in North Korea to pretty much anywhere in the US.
KP has been telling people they have a working hypersonic ballistic missile (travel time Korea to the west coast at ~ 1hr without going sub-orbital.)
The US and KP are technically still at war (the Korean war stopped with a cease fire, not a treaty) and the US and its allies levy sanctions on them that hurt.
So while in previous tests it was both not widely believed that KP could reach the US and the KP had not said they could reach the US, both of those positions changed. That changed the threat posture from "zero" threat to "some" threat.
Fortunately physics is physics and it's pretty clear after 10 to 15 minutes what a missile is doing and what it might be able to do.
As a result I don't really think this was a "knee jerk" decision, I think it's likely policy going forward until better clarity is available on how rapidly KP's missile technology advances and an effective counter can be put into place.