Something about Viktor gives he's into dry humping. That art is not lost on him at all and it's something comfortable if his partner meets him half way on. I do think he has a relatively low and borderline non-existent sex drive but will rub up against his partner as a means of initiating something when he wants it. A very subtle shift of hips or excessive touching of your clothes or fuck me eyes from him. He seems like a very reserved and subtle man so his flirting of course goes that way. I think his biggest hurdle to initiate sex stems from he's terrified he may come off as creepy or a harasser given he is from Zaun and has had a rude awakening of how Piltover people assume his romantic actions.
I might rewrite this or expand on it later but just some fleeting thoughts