The washers are part of the blade locking system you need them and are part of added weight [ 5 gr ]
However if you tighten the Striker heads very tight [ as all heads should be ] ...the 100gr thin washers can be dented...so they supply spares...
the 125 grain has a solid heavier brass ring ...that adds that 25 grs to make the 125 gr head so they dont use the spare thin washers...
JMHO
Neil