I’m glad to see this. The shutdown has been too “business as usual” for most Americans, while others are expected to work without pay, which is ridiculous.
Strictly speaking, their pay is delayed - they will be paid for all the work, eventually. Still, regular employees should not be going through this, though.
The reductio on this argument ("why not just pay them for the year in a lump sum on December 31, 2019?") makes it obvious how inadequate it is given two pay periods have already been missed.
There are real financial costs being created (late fees, etc.) that the government is offloading onto its employees. This is dishonorable.