Question about the Routine de Matin exercise

In the Routine de Matin (Futur Proche & réflexive verbs) exercise, I used the present indicative tense in the following sentence (even though all the other answers were in the futur proche) because it made more sense to me: “Pendant qu’il SE PRÉPARE avec toi, je vais .....”. 

It was marked incorrect, but doesn’t it fit the sentence better? It said that it should have been “Pendant qu’il va se préparer avec toi....”. 

Thanks!