I don’t know specifically about the one segment question but my experience is that I see upgrade offers until I request a SWU and then the offers disappear. You could try to unrequest the SWU and then upgrade your outbound and then call to request the SWU afterwards? They seem to mostly be clearing the SWU within a day or two of departure so I don’t think it’s too risky that you’d miss an upgrade during the window in which you cancel and try to do a paid upgrade.