Yes, it's a bug. I hope. In the Euro forums, a blue said they were looking into it, but we can't get a blue to comment here. Which I don't understand, as so many people have already made posts about this. Please, could we get a comment from a blue?
It looks like there was a little confusion on this topic, so allow me to clarify - there is not a bug involved here.
Required level is not the same thing as an item’s power level, and it definitely does not mean a level 69 character should feel uncomfortable about using an item that specifies “Requires Level 61.” Items saying "Requires Level 61" on them is by design. The item can be at a power level intended for level 68 or 69 characters but we let players use it at Level 61 - this is intentional.
A primary boon of this approach is you know that items you find early on in your leveling experience (around 61-62) aren't replaced immediately upon reaching 63. That awesome item you found at 61 should be able to stick with you up through 69. When there are too many tiers of items, you transition through them rapidly and the items start to feel transient. Why bother gemming or enchanting an item if you expect to find an upgrade in 30 minutes? The Mystic’s Enchanting is powerful, but it doesn't feel worth using if you don’t have confidence your item will still be useful in 2 levels. Another benefit of this design choice is that it is alt-friendly. We think it's really fun to have the option to twink characters. Why not allow items you find at the upper echelons of the 60's to be passed down to your new characters fairly easily?
This does have some downsides, including that upgrades can feel a little sparse between the latter levels before cap (66-69). However, in this situation, we felt the benefits outweighed the detriments and it keeps the element of randomness that we feel is core to the Diablo experience. We want to ensure there is a chance to find an amazing top tier item the moment you ding 61 and get to hold on to it for hours if fortune smiles upon you, though that may mean it takes a little longer to find an upgrade for that particular slot.