Unlimited gives you ad-free streaming on the desktop version.
If you also want to use Spotify on mobile devices such as smartphones or tablets, you need a Premium account.
I'm pretty sure it was always like that, so no recent changes there. 😉
P.S. In the US, you can use the mobile version also without Premium, but only for the radio feature.
If you are in the USA, free/unlimited accounts have access to mobile radio but not playlists.
Everywhere else requires premium for all mobile features!