Some are and some aren't.
That one is actually a revamp'd Performa 650 that got some bad press. The revamping fixed some issues with the unit not being able to output near its rated watts when hot and this new unit does pretty good. By revamped I mean its the same design they just switched to better compnents and labelled the unit in line with what it can actually handle.
I give props to Rosewill for making changes to improve a product rather than leave a so-so unit on the market.
^ no it means that some are old but not yet "revamped" or still good for lower powered systems than the wattage listed, if your system uses 500W and you get a 450 or 500W psu, usually it wont be able to handle it regardless of brand...