I agree that there was no real evidence that either relationship was that deep for him, but conversely there's no real evidence that it was only 'shag' or would only have been a shag (in the case of Gwen) either or that he was interested in shagging every member of his team. That's just personal interpretation because the writing was vague and subtexted or weak enough that if you want to you could chose your own adventure depending on your own biases.

Plus RTD's idea of what is 'romantic' and I use that term loosely and not really in the hearts and flowers way seems to be very different from what I, and apparently a lot of other people, consider 'romantic'. He seems to like the idea of the cool, aloof dominant figure and the needy, dependent figure as romantic model so it's possible in his mind we were supposed to see a 'love' story between Jack and Ianto in COE and it just got lost in translation and/or weak writing.