For Tier points
For Europe A/Z/W/T are classed as discounted fares
For TATL A/Z/W/T/O/R are classed as discounted fares
U is business redemption
For reference in GC W/Z/A/U/T didn't qualify
EI did change the fare buckets around a few years ago, but I've certainly travelled on X fares recently on a revenue basis