Totally understand the confusion - I've fielded this question a couple of times already.
So, the system we implemented where we tag every game as a single genre was introduced back in April, but we do it manually every time which means that there's been some ad-hoc forming of policy in this as we've gone a long.
Through the Ages
and Race for the Galaxy
are prime example of this - When Through the Ages
was reviewed, I don't think we actually had a 'board game' tag but like you say it can be identified as a card game. By the time RftG came along we'd created a boardgame tag and the decision was made to class ALL physical boardgame ports as 'Board games'.
The main point for this year's awards though was to make sure that a game just came under one category, which was achieved. We've been a bit inconsistent with the tagging, sure, but I don't think you can say we've got it 'wrong' (apart from that thing with Darkest Dungeon
... but we don't talk about that...
We will do better for next year, at least in terms of consistency, but I'd rather we didn't detract from RftG's win by getting bogged down as to what get's tagged as what. At the end of the day, you guys still voted for it.