I checked the schedule for that date. There are only 10 trains eastbound from Elizabethtown as opposed to normal 13. 644 is not listed. How has ridership been on the Keystones? Many people that took the Keystones from ELT and Lancaster were commuters to/from Philadelphia. So, with more businesses deciding to keep teleworking, that could drastically affect daily ridership—thus the need for cuts.
It’s interesting to note that even in February, there are only 9 Keystones plus the Pennsy in each direction. So, I am thinking this is taking effect after January 1–possibly due to reduced ridership and staffing issues.