can't speak for suse, but i'm glad it's not just a 'buntu thing.
however, in xubuntu/ubuntu/etctu, there is no root account per se, but you can sudo commandshere or sudo su. then you have full root-like capability, but since there is no root password, you use the user account password to gain sudo access. when i put it that way, it sounds like a really stupid idea, but it's my experience (and perhaps misunderstanding) based on using 'buntu for a year or more.
in tinycore, you can already set passwords for both root and tc, and presumably other accounts, so when you say "it's not multiuser" i feel like it depends what your definition is. i don't think the package system (that's relevant) is multiuser, or probably a number of other things. but it's linux, and it has more than one password and more than one account. so i would think, user or tc password to login as user or tc, root password for access to sudo.
but naturally that's hypothetical and depends on whether people (including roberts) wanted to make it that formal by default. i remember using the "secure" boot option in dsl which asked me to create passwords, but it never asked for them again, even when using sudo. i don't understand why, but someone probably does.