Ianto's utter acceptance of what Jack lives with -- and Jack's gratitude for that, especially after the bitter exchange with Alice -- is, for me, a defining moment for them. Ianto's clearly making a choice here and Jack gets it. (No way can we get from here to any scenario where Jack sends Ianto away or retcons him for his own good.) Ianto's also carefully feeling his way into understanding the limits of his own agency, to a much greater degree than he did in The Dead Line -- although I think we can understand that as backstory for what happens here.

Totally agree with you about switching, btw. :)