When testing the block step rates, my test was slightly off (~$14 in the month of July). The root cause of the issue is that the utility rate code in ur_calc_timestep (net billing and buy all / sell all) is only allowing each hour's energy to be given to one tier. See below screenshots:

and the resulting charges:

These are different from net metering, which accurately allocates all kWh in one tier before moving on to the next tier.

See attached SAM file:

evenly_distributed_tiers_test.zip

Update ur_calc_timestep to split the kWh appropriately.