Nope, the "7 days free" wasn't a a trail but 7 extra days when you purchase a full year subscription. I was considering to get a monthly subscription to try it out but since they tried to trick me into a yearly one I simply decide to Torrent the crap out of their content. Sorry not sorry.
That's one of the things that's great about Apple's iAP and Apple being the handler of transactions. There's no tricks, it's standart on every app: If there's a trail period you get the trail and if not you directly start paying. Also no tricks in the cancelation process, it's all in one place so you can review and cancel easily. You can also change plans right from the same screen. If somehow you manage to purchase something you don't want, get refunded easily.
I really hope that if Apple is forced into allowing 3rd party payments, we end up getting a standardised interface like the one we have currently on Apple's platforms but with an option to choose the alternative payment method(in the same screen but a different card or account kind of thing, like choosing a card in Apple Pay).