That's a little confusing, though, isn't it? A blinking regular yellow light means "you have the right of way, but proceed with caution". But this blinking left arrow would mean "you don't have the right of way, so proceed with caution". The distinction may sound subtle, but is quite large.
"blinking yellow left arrow" is the same thing as not having a protected turn at all.
Not quite. Yellow blinking left arrows are always for a protected left turn lane. So when blinking, it does become more like an unprotected 'turn left on green' type of light, but you don't have the straight-through traffic coming up behind you, since you're on a dedicated turn lane. And the yellow flashing arrow is usually timed so that it happens at the safest time to make an unprotected left.
But it cues your brain that it might not be safe to turn left.
this is a change that's already rolling out nation-wide