According to Biana, Tam was oblivious to flirting.
He didn't even know how it happened.
"I swear Bia, she means nothing to me, I love you."
Now if he'd continued with the charade Alvar basically forced him to create, he would be trying to sell it.
But Tam honestly hasn't seen it coming. He was falling for Biana, and falling fast. Falling so fast that he wanted to end it and save her, but he loved her to much to let her go.
Maybe he was just being selfish.
He meant all the words exiting his mouth. Glimmer had just come up to his locker and started talking to him, and he thought nothing of it.
But according to Biana she was flirting.
Finally, he tried a different tactic. "This is probably not what you want to hear, but it kills me to see you sad. And you look really cute angry."
That cracked her.
"Seriously Tam. That was straight out of a cheesy romance movie." She hugged him.
"You're favorite kind right?"
"You know me so well. She really means nothing to you?"
"Of course. I love you, remember?"
"Yeah. Just don't die, then I'd have to be extra sad."
"You want to watch Five Feet Apart now don't you?"
"You know me so well."