As far as I can see, there is a mismatch in the max_rpcs_in_flight and max_mod_rpcs_in_flight value ranges.

According to the LOM in section 39.4.5.:
max_rpcs_in_flight: The default setting is 8, minimum setting is 1 and maximum setting is 256.
max_mod_rpcs_in_flight: The default setting is 7, minimum setting is 1 and maximum setting is 256.

However, when considering the following information, above cannot be correct: The max_mod_rpcs_in_flight value must be strictly less than the max_rpcs_in_flight value.

So max_mod_rpcs_in_flight can only be in the range 0 to 255 to be lower than max_rpcs_in_flight. If the value cannot be 0, I would expect a range of 1 to 255 and as a consequence the range for max_rpcs_in_flight cannot be 1 as it should be greater. So the range should be 2 to 256 if I am not mistaken.

Summary:
max_mod_rpcs_in_flight: 1-256 (current), 0-255 or 1-255
max_rpcs_in_flight: 1-256 (current), 1-256 or 2-256

In case the min and max values must be changed, the validation script for these parameters may need to be updated, too, to prevent misconfiguration.

If my understanding is wrong, then it may help to add some additional information to the manual instead.