Is it true that frequent wakings in the night means baby tends to be more intelligent?

That's clearly a myth. Most babies experience frequent night wakings. Babies have shorter sleep cycles, and they spend proportionally more time in “active sleep," the baby equivalent of REM. They also have smaller stomachs, which means they need to eat more frequently than adults do. Put these traits together, and you get a creature that sleeps lightly and needs to awaken every few hours.