I understand what the guy is saying and you can't take what's he's saying literally. He's using philosophical language.
Look at it this way. Say your father is the most loving, kind and gentle person you've ever met. He's very supportive of everything you do and, now that you're an adult, he speaks 'with' you instead of 'to' or 'at' you. You love and respect him for all he's done for you as a father. He works for the government and doesn't talk much about his job because it's of an incredibly high security nature.
Now say that same father is head of a special forces unit. He's a badass that can take down an enemy unit armed only with a toothpick and a wetnap. His orders are curt, to the point, and he expects them to be followed rigorously and to the letter. He does not suffer fools lightly but is fair and offers praise and recognition when it is deserved. He leads by example and action. His troops love him for all this because they know he's the best leader they can have. He doesn't talk much about his family life because he's old school and prefers to keep distance between himself and his subordinates and keep his family life separate from his job.
Your father is ontologically the same person to both groups, but loved (dare I say, 'worshipped') by two distinct groups who have completely different ideas of who your father is, yet the particular reason why they hold him in such high esteem is important to each particular group. From the outside, one can ask, "Is he how his children view him? Is he how his soldiers view him? Isn't he both at the same time?"
What this professor is trying to say is that God is a PERSON whom two different yet related religious groups view differently and worship accordingly. Now, as Christians, we say that know who God is (as much as humanity can know) because He was revealed to us through His Son, our Lord, God, and Savior Jesus Christ. WE see our father (in the above example) as both. But Muslims only see one facet.
And I'm not trying to say it's in a modalistic manner, but something more, something deeper.
I've long thought this way about the question, "Do Muslims and Christians worship the same God?" My answer has been, "Yes...and no," because, as I've argued when asked this question, "Because no Muslim would dare say that Jesus Christ is God and that is at the crux, it is THE fundamental crux, of the question what separates Islam from Christianity."