My guess is that the hopped lme's age allowed the hops to age as well. Some hopped extract has been boiled to some extent, so its like having a concentrated wort aging in a can.
As hops age, alpha acids reduce and beta acids remain. They offer less bitterness and don't taste as prominent.
Hopped kits are not worth the money. If you can measure the weight of the hops, and drop them into the pot, you can use plain extract and hop the beer yourself. Now you aren't tied to some manufacturer's unknown recipe like a ball and chain. At some point, you'll want to create your own recipes (or start with others' and tweak to suit your tastes) and at that point, you will be able to freely choose what to tweak, because you will know exactly what is in it.
Similarly, amber and dark extracts are just as mysterious. You don't know what the manufacturer put in there, so you'll never REALLY know how to convert your recipe to AG or how to properly tweak it.