I can't always tell I'm dreaming when I'm dreaming, but I can always at least tell it's reality when I'm awake. Apart from that one time I was concussed when I fell off my bike as a kid. And the slew of drug-addled experiences as a young adult, but I'm not sure if they're considered reality or not.
Language evolves, and it's now completely normal to use an adjective in place of its adverb in some sentences, particularly when it's being used for emphasis
Entropy