If you are on an IFR flightplan then of course you log IFR
I would have thought not if you are not actually IMC, that's the case here. Flown on an IFR plan from LAX to MIA and didn't see a cloud the entire time, severe clear VMC the entire time, certainly hope the crew didn't have the audacity to log it as IMC. Not seen a log book that had a column for "IFR", only "IMC - flight or ground"