Are there certain classes that have no AQM?

PARTNER DATE ACTIVITY DETAILS BOOKING CLASS AQM AQD
Jul 02 2016 Air Canada 1180 Vancouver (BC) - Toronto Pearson (ON) B 0 $287.89
Jul 02 2016 Air Canada 8 Hong Kong (HK) - Vancouver (BC) N 0 $882.10
Jun 25 2016 Air Canada 015 Toronto Pearson (ON) - Hong Kong (HK) S 3,896 $1,079.00

The B and N flights are showing 0 AQM but AQD. They were prem economy.