The USRBDX and USRYIELD card were used to tally triton current from one region to the other,
the results from the two card is different, it is showed below:

by the way, the probability of triton among polar angle 0 to 30 degree with all energy by one primary is 3.27E-3 for USRYIELD card;
and 2.76E-03 for USRBDX card;

To come back to your plot, in the case of the USRBDX, it has been integrated integrated over the solid angle (as explicated by flair). Then is you divide by you solid angle 2pi * (1 - sqrt(3)/2) ~= 0.8417872144769, you obtain the same curves.