My thought on the concept of auth hold vs post hold... it's not a transaction until it posts, yes. But I believe elsewhere in the Reg it is stated that to escalate the liability to $500 (or unlimited in extreme cases when the fraud goes on for over 60 days), you have to show the transaction could been blocked.
The question I might ask here, is if the auth occurred during the tier 1 liability window but the cardholder notification and posting of the transaction occurred in the tier 2 window, would you have been able to block that transaction? Probably not, without the aid of a time machine. But I believe that is not necessarily a black and white answer.
I think Reg E could benefit being brought into the year 2024 where we live in a world of real time transactions, but also real time transaction notifications.... but that is another matter.

We keep running into situations where the cardholder doesn't notice "subscription based" fraud going on months and months because they "don't have time" to review their activity closely (despite logging in their online banking etc) ... but of course "whoops I don't have enough time to look closely" is not really addressed in reg e as a detriment to the cardholder dispute process.... other than the tier 2 tier 3 liability if it drags on for an excessive amount of time.
Increasingly, we see more and more scenarios where I'm calculating tier 1 vs tier 2 vs tier 3 becaus ehte cardholder just doesn't care.... and that gets really ugly if I take the examiner's opinion they expressed as-is. A lot of these subscription things though are small enough that tier 2 liability doesn't even wind up exhausted. Death by 1,000 cuts.