That is from the example. But this use case is not something I can imagine happening a lot. But my imagination is limited.
You would have to know before, what bonus items you would want. Sure, there are people buying the deluxe version of a game upfront. And you might use this as an incentive for people to overpay.
But the games I browsed practically never use it this way. And some even have several tiers of bonus content. They are the worst, but only because there is no way of increasing your level.
Itch should overhaul this system. At least with more clarifications at strategic places. While some do not like the term "dlc", this is what it does, this is what it is used for and this is what it should deliver. It does in some special cases, but fails in others.
Oh, and the reason why I assumed the tier is calculated with the discount is the message you can read when going to a purchased page. It remembers your paid price plus the discount. So the information would be there. So it would read for example like this: "Purchased for $4.99 1 year ago (50% off)". But it is just assumptions.