All those Line Duty Allowances, Ground Duty Allowances and Duty Free Commission were being taxed all these years.
But it's just that CX didn't include all these in calculating the holiday pay (including annual leave and statutory holiday)
Outport Allowance has already been out of the scope for long (since cabin crew didn't appeal for that after the ruling of Court of Appeal). It wouldn't be treated as wages and so wouldn't be taxed.