You MAY be right--or you may not know the entire story. You are assuming that everyone already has a full month, THEN they are putting in WS. I know guys that will drop their schedule to very low (even zero) then put in a GS first thing. Once they have secured their GS, now they need to get the rest of their flying up to the trigger in order for their GS to pay double.

In fact in our pre-PBS line of time bidding days, I flew with a very senior captain who did just that. This was also from the time where a pilot got two GS in seniority order before a junior pilot even got one (I am glad we changed that, by the way).

He would use a tool called an "empty moveup" (pre-PBS) to start out his month with a value of zero. He would then get his two GS, then do nothing but WS easy turnarounds or two day trips. He did this for years.

So perhaps some of these guys white slipping that you are observing are doing something similar.