MV Switchgear Insulation Voltage vs Altitude

If an MV switchgear has an operating voltage (or system voltage) of 11kV and it is installed at an altitude = 1600m above sea-level, what should its insulation voltage be i.e. 12kV or 17.5kV (according to the IEC standards, say IEC 60694)?

The thing is; IEC 60694 standard seems to suggest that for attidues greater than 1000m above sea-leve, the "V_insulation" should be multiplied with a K-factor (=1.08 @1600m above sea-level). To me, it sounds technically inane to apply the K-value to the insulation-voltage (which is independant of the actual voltage at which the switchgear is operated). With this in mind, isn't this standard suppose to "prescribe applying the K-value to the "Operating-Voltage" instead?

For me this would mean that my 11kV switchgear needs to have an insulation voltage = 11kV x 1.08 = 11.88kV, thus 12kV. Instead of applying it to 12kV and having to go for a 17.5kV switchgear.