You are right, this is exactly why I added this line.
Using a correct syntax, I get this:
Warmup
-5m ramp 50-80% 85-95rpm
2x
-10m 80% 85-95rpm
-5m 40% 85-95rpm
Cooldown
-5m ramp 80-50% 90rpm
Test.zwo (906 Bytes)
Note, how the cadence ramp is not available in the warmup and cooldown power ramps.