Because we're in the middle of the second-pass portion of the project to ensure we haven't missed a prime below n=5M.
First-pass testing has got to 10M and it has been decided that we should finish second-pass (also known as double-check) up to 5M.
This work has already resulted in one missed prime!
To go on to the next stage we need two matching residues for every outstanding test below 5M.