No. "Only for that purpose" means that you never use it. This is trivially detected: the OS event logs will report that it hasn't been booted in 6 months, and no files have changed in that time. It's obvious that you haven't been using that system in the time you were out of the country; why did you have it with you?

For this to work, you need to actually use the dummy partition for non-sensitive matters -- and be absolutely religious about separating the sensitive tasks from non-sensitive, which is much more difficult than it first sounds.