Regardless of what the column heading in a commercially produced logbook says, the requirement in the UK (and I suspect Germany is the same) is to record "information about any special conditions under which the flight was conducted, including night flying and instrument flying"
Instrument flying means flying by reference to instruments, which is not the same as the flight rules. Probably commercial publishers' inability to understand the difference between IMC and IFR is at the root of this problem! Although similar mistakes occur in some RFM's I have come across!