Logging IFR time is pointless. However logging IMC time does show some sort of currency/experience, which is what I understood that column to be for. Some countries (NZ? Aus?) require x hours in the last 90 days, or the like, to maintain IMC currency.
That said, I cant be bothered starting the stopwatch every time I enter cloud, so I just log 0.1hr per sector, which I reckon is pretty close, on European short haul. And it makes counting your sectors really easy!