Oh, he caught it. It just wasn't new so he didn't remark on it. Perhaps because he has actually had more in-depth conversations recently with Spike than he has with Ianto (now that he thinks about it), he has actually caught on to this fact about Spike already. He just never realised it applied to Ianto too!
He nods. "Okay. I'll try, at least." A little grimace. "I've never really known what to say to people when they're having problems. I know sometime it does help just getting it off your chest, but after that... I never know how to follow it up. I guess perhaps I do try to avoid bringing things up again because I don't know how to help them."