Strictly speaking, the dot in the latter space isn't actually necessary. It needs to be a resolvable domain, but if you bought a TLD you could be "name@tld"
(Obvious caveat being that any provider can trivially append @provid.er if you don't specify, so this isn't really proof that email is specified that way.)
And if you try to actually use a bare TLD you will crash hard into collisions with unqualifed domains and search paths. So, fun as a hack to amuse fellow techies but not useful for anything real.