NES Dev Wiki wrote:
This results in a pseudo-random bit sequence, 32767 steps long when Mode flag is clear, otherwise 93 steps long (the particular 93-step sequence depends on where in the 32767-step sequence the shift register was when Mode flag was set).
I did a brute force checking of this fact, using the algorithms supplied on the wiki. It seems there are 31 "seed values" that result in a 31 step sequence instead of 93.
The code can be found here. I'm just making sure this is correct. If so, the wiki should be adjusted to mention it.
There is no such discrepancy for the 32767 step sequence.