The second Age is the time of the fall of Numenor, the Elvish split over Sauron and the creation of the Rings, the setting up of Arnor and Gondor and the Last Alliance.
There's political intrigue, world altering cataclysms, gigantic battles, betrayals, power... Quite a lot of fodder for great TV.
Which is all an rough outline of events that happened over hundreds of years. There is very little down on the ground or character stories for Second Age canon.
In other words... Them placing it in the Second Age, is basically them all but coming out and saying that they're wanting to turn it into a GoT clone wearing a Tolkien skin.
Adherence to "canon" isn't really that important. What is though, is adherence to the spirit of what is being adapted, and... There just isn't very much to WORK with in the Second Age. As it was more summarized then shown.