Free-to-play exceptions reign, like other platforms

Platform holders have a history of excluding certain games, including free-to-play titles (which may or may not have optional subscriptions or microtransactions), from the scope of their subscription-based services.

In other words you can download a free-to-play game and still log in and play without Xbox Live or PSN Plus. There was some contention initially from companies like Microsoft but eventually publishers smoothed things over. As it turns out Nintendo is following suit. Confirmed to Variety, Arena of Valor publisher Tencent explained that the Switch port won't require a subscription to Nintendo's online service. As a refresher Arena of Valor is a wildly popular mobile MOBA that's now Switch-bound.

Even if you aren't excited at the prospect of this particular game it's great that the floodgates for free online play are open almost immediately with a big publisher paving the way.

Tencent’s ‘Arena of Valor’ Hits Nintendo Switch in September [Variety]