This is definitely true, I would focus on how hasty romeo is.
The main point is where he sees Juliet at the party and says 'did my heart love till now?'. This comes right after his long petarchan soliloquy which focuses on his mourning over losing Rosaline.
He spends a whole scene moping over her, but the moment he sees Juliet he has forgotten all about her. This is just one example of his fickle tenancies, and makes the reader question whether he ever loved or was it all just lust?
Another example is that in the first scene he discusses his hatred for violence, yet after mercutios death he murders tybalt without haste. Romeo becomes increasingly fickle and unpredictable as the play progresses.