Strongly disagree here. Datasheets are vital communication from your suppliers as to how a part will work. If the datasheet says 1.5GHz, it will work at 1.5GHz (as long as all design criterea are met). The data available from Ti doesn't just show "a general impression of things", it shows everything I'd need to design that SoC into a product. Not only the datasheets, but I can get the app notes, design guides, order development kits, etc.
It may work at 1.8GHz, but they won't support it in that configuration. Can it be underclocked? Absolutely.
When chips are binned, you don't sell them as the same model number. You give them a different designation. They'd sell these as OMAP 4445, or something, not call it a OMAP 4460.
For example, you don't buy a Core i7-2600k and expect to to run any different than it's datasheet specifies. It may run better, but it can't run worse or it's defective. Chips that don't meet that spec may be sold as a Core i5-2500 or something else.
There are plenty of vendors that don't post datasheets online, and you either have to register (so they know where the info is going) or you have to make direct contact. That's common as well, but typically for more complex assemblies, not component parts.
