It's most likely the opposite. People have no idea how to keep their desktops/laptops secure and it is much worse then it comes to the mobile area where apps can have access to almost everything. Another problems would be apps that carry hard to remove exploits (tends to happen in android). It is not possible for a smartphone to be safer than a Linux machine solely dedicated for a wallet, running behind a hardware firewall.
I wouldn't say the opposite but the most important information here is that nothing is really safe if you don't know what you're doing. Android or apple phones may be safer than a windows PC in most instances but you could still download a dodgy app or get some virus from clicking a dodgy link. People could also lose their phones and if they haven't got a back up then they're screwed either way. My advice is to just know what you're doing and protect yourself and back up as much as possible in case something goes wrong.