I'm not sure where you read that but Omnisphere is one of the best synths I have just because it has both the option to use the awesome preset library that comes with it plus the ease of use if you want to make something from scratch.
Omnisphere has both sample based and subtractive oscillators (through DSP) like most other synth. It can also do sort of FM. So it's bull that it only has sample based oscillators.
You can make the simplest thinnest mono sound you want all the way up to massive effect drenched stereo sounds.
It's easy to get carried away. But it can do simple sounds as well.
You won't regret getting it. I haven't. Sometimes you need those big sounds to compete with the rest of the guys out there. A client can ask for a very typical soundscape. Omnisphere makes that easy for you.
As you've probably understood by now, I love Omnisphere. Hehe.