I think there's historical data showing that Nintendo consoles in general are more commonly owned by PS and Xbox owners, as opposed the "opposite" console in that rivalry. I don't think this is indicative of Switch being a default secondary console as such, but rather a result of Nintendo having a very different library to the "twins". It makes much more sense, from a perspective of software breadth, to purchase a Switch to go along with a PS or Xbox, rather than a counterpart with very similar offerings and formats.
Obviously, the Switch is the primary system for a majority of gamers on the platform, I don't see how it could have sold as well as it has if this wasn't the case. If anything, with associated costs of consoles and gaming in general today, I wouldn't be at all surprised if the number of multi-console ownership has declined sharply over this generation.







