Well, The iphone support must be for very early versions of iOS, the current versions are not supported.
No, it has never supported direct syncing of an iOS device (bypassing iTunes). MC does support direct syncing many older non-iOS "regular" iPods. Apple does not allow this for iOS devices, and if JRiver hacks it (which would be possible but not trivial) Apple could break the support at any time with a point release.
There is an option in MC (File > Export to itunes) which exports the current playlist or view to itunes, and you can then sync.
If they refer to iOS support for syncing anywhere in their marketing, then that's what they're referring to. Also, incidentally, if you want to keep MC and iTunes in sync with each other, pointing to the same set of files on disk, there is a really nice and actively maintained plugin
from Prod called MCiS.
MC does also support iOS in a few other "ways". The built-in WebGizmo feature now works pretty darn well for Audio and Image playback support from a MC Server over the air (video support is a not-yet item). If you prefer a native app,
JRemote is making leaps and strides (and the developer has said he intends to support playing back as much as is possible to the device, rather than just "remote" mode, as soon as is possible).
Frankly, if JRemote could stream my music from MC at home over the air to my iPhone, maybe caching local copies of files it streams for later playback? I'd pull the "Music" app out of the dock and replace it with JRemote, and then I wouldn't ever sync my phone with iTunes again. And he's working on it. I haven't checked in on
My River in a while, and I prefer JRemote, but that's another popular option.