Hi! I found MAX7301 behavior that differs from what is indicated in the datasheet. Reads and writes to the multi-pin registers that write to fewer than 8 pins at once return data differently than documented (see highlighted line).

When reading from this register, I saw that bits D4-D7 were the ones that were data bits, and D0-D3 were read as 0. Similarly, for the 5 ports 4-8 register, D3-D7 were data bits and D0-D2 were 0s.
However, when writing to this register, it appears the documentation is correct and bits D0-D3 must be written to be applied to ports 4-7.
Might need to update the documentation / specify this discrepancy in the datasheet!