Is ノーマル customary in reference to being straight

I was recently watching an anime and one of the character, in reference to him being straight, said:

僕はノーマルなので

(in case I misunderstood, this is from Eromanga Sensei, ep09 at around the 6:30 mark)

I got curious and tried to research whether this was the usual way to state that someone is straight but couldn’t find anything. I know ストレート can be used in this context.

Did I completely misunderstood what’s being said?
If not, is this commonplace? Is it considered acceptable or rude?
If this is considered rude, what would be the acceptable way so saying I’m straight.

Edit:
For context, it’s been an on-going thing on the show that Kunimitsu (the character I quoted above) thinks the main character (Masamune) is gay. During the scene I’m referencing, Kunimitsu is offered to share a bedroom with the main character to which he object.