That’s an odd assertion to make when the full pharmacodynamics and mechanism of action are unknown. Modafinil doesn’t increase your cognitive performance in the way that a substituted phenethylamine would. Focus and attention are certainly related to wakefulness, but wakefulness in and of itself doesn’t increase cognitive performance.
Substituted phenethylamines[1] are derivative compounds of phenethylamine. Many substituted phenethylamines are stimulants, while some are psychedelic too. Dopamine, epinephrine, amphetamine, pseudoephedrine, MDMA, and many others are considered to be substitued phenethylamines.
Modafinil interferes with sleeping less than other drugs - it's only a problem if you rely on the "crash" of running out of energy over the day to fall asleep.