> Wouldn't "equivalent intoxication" mean the driver in both cases equally shouldn't be behind the wheel?

No, "equivalent" here is general-purpose intoxication, not something calibrated to driving. Since the effects are so different, we should expect significantly different levels of driving impairment to be likely.

What is this based on?

That the drugs work in very different ways so we shouldn't assume they have the same intoxication profile? I feel like that's basic knowledge.

For where I say we're looking at general purpose vs. driving-specific, that just seems to me like the most reasonable statement they would have been making.

I think the confusion might lie in the use of your term "equivalent intoxication" then. Especially when you then mentioned their different intoxication profiles. How exactly would you define equivalent intoxication levels in something with different intoxication profiles?

Not my term, but some kind of test might make sense, or the average of several things. I mean, how do you define intoxication levels at all? You can't just, like, measure reaction time and say you're done.

Yeah it's not easy with alcohol either. Many people have almost no impact on their cognitive abilities or reaction times with a BAC of .08, while others could be legal to drive with a .06 but shouldn't be.