If a team wanted to mask their lap times during a test they could work it like this....
Do a five lap run... on lap one the tires and systems are warmed up etc. Lap two begins with an all out assault on sector two but they start a corner before sector two so the corner entries are real and not compromised to affect the whole sector time. The rest of lap two they could go at 95% and then begin an all out assault on sector one, again starting a corner early to keep things faithful to what they would encounter during a race or quali lap. Then they would go at 95% for sectors two and three before doing lap four where the all out assault would be on sector three. Then lap five would be a whole lap at 95% effort. So you have a five lap trial with three hidden "golden times" which you can assemble for an idea of the car's pace over a complete lap and few opposing teams would be able to interpret the times unless they had full knowledge of the intent and effort spent. This way they could have a "composite lap" of the three hot sectors for purposes that would aid the engineers.
Surely this must happen all the time. I can't be the first person to think of it.