"- I'm sure you could. But he said he's not. Good enough for me."

Cal's tone indicates that he's not playing anymore. The friendship with Ianto is comfortable and uncomplicated by sexual bullshit and he really needs it to stay that way. He's more than got his hands full with the confusion that comes with Sam.

For that matter, he's just as soon avoid any circumstances in which Sam might offer a list of Jack Harkness's virtues, though he's not currently acknowledging that as a reason. Some things you just don't think about.