FedEx may have delayed his go-around to see if the razor thin spacing that Tower controller caused by issuing the take-off clearance to SW would work out. This happens often in VFR conditions, NEVER in Cat 3 conditions because……drumroll please………you can’t SEE the jet in front of you. The FedEx Captain knew the spacing with SouthWest was suspect, and from the subsequent conversation and confusion between tower and SW regarding where the SW jet’s position was in the takeoff sequence. At that point, The hairs on the back of the FedEx captain’s neck probably prompted him to Go-around. I’m not sure why he didn’t off-set from the runway centerline just to give himself an increased safety buffer from SW’s projected flight path. The Tower controller seems to have made a totally unnecessary error to expedite traffic flow, at a quiet airport, by issuing SW a takeoff clearance in CAT 3 conditions. The SW crew, if they knew that FedEx was on a 3 mile final should never have made the radio call to Twr that were holding short, ready to go. Tower thanking FedEx for his “Professionalism” was his attempt to hopefully avoid a report of the incident, and also perhaps, acknowledgment that FedEx saved the day, and averted a disaster. If the Southwest crew knew FedEx was on final, they should be having “Tea and biscuits” (as you Brits like to say) with their Chief Pilots and the FAA. I’m sure there will be no tea and biscuits for the Tower controller.