You're right.
Motorists need to A) see a vulnerable person AND B) react appropriately.
Hi viz clothing helps to achieve A) and also can give a little extra time for a motorist to achieve B).
That seems like a good thing. It hardly matters whether it's more or less important than being aware of what's going on around you. Both are good things.
I'm not really saying wearing hi vis clothing is a bad thing but more that distracted drivers are.
Lots of times drivers see something, but their minds don't register that something is in their path and they better do something or they're going to hit it.
A driver may be sitting at a side street, waiting to enter a roadway, see a rider coming down the roadway, the rider is visible and has the right of way, but go anyway. Same thing with a driver waiting for a left turn or even immediately after overtaking a rider making a right turn in the riders path as if the overtaken rider suddenly ceased to exist. These are all very common scenarios.