Migraine-associated vertigo, can this cause severe lightheadedness as opposed to actual spinning or dizziness ?

Sure it can: While the most traditional & specific definition of what is known as vertiginous migraine or as you say "Migraine-associated vertigo" is that of actual vertiginous sensations or spinning/whirling/tumbling/moving feeling either followed by or preceded by migraine headaches there's nothing that says that a person couldn't simply have an event of lightheadedness or disconnected feeling & headaches.