Rider Switch on May 26 for Big Thunder Mountain had end-of-day and Splash Mountain on May 27 has end-of-month; so not change from OP for those rides at this point.
I wonder if it really makes a difference as far as processing riders. From a customer standpoint, going to the end of the month can be helpful. I'm guessing that people are giving away or maybe even selling rider switch passes and the utilization of Rider Switch for Flights of Passage, Seven Dwarfs Mine Train, and Big Thunder Mountain are higher than the other rides. And, Disney is trying to cut this down as they expect a certain percentage to never be used. Maybe locals save them up and have an end of the month rush?
This is all speculation on my part; curious to understand WDW logic on this.