I've certainly heard both. For a lot of people all their connected devices at home are wireless: smart devices, phones, many have laptops rather than desktops,

I've certainly heard both. For a lot of people all their connected devices at home are wireless: smart devices, phones, many have laptops rather than desktops, tablets, …, and while out the connect to other wi-fi networks. It is easy to circulate WiFi and cellular data access, and if you don't use much or any wired networking at home all your normal network access is therefore WiFi. Screensaver as wallpaper is more rare but I have heard it, and have done for some time (I know non-technical people who have used wallpaper and screen saver wrong for many years, going back to when fancy screen savers were more common than simply powering off, either calling both by one name or just using them randomly). More common these days though is people simply not knowing the term, except to confuse it with a physical screen protector.