Comment 1 for bug 1884220

It's unclear that that's the right expected behavior.
Firstly, the subtraction is necessary because of displaced strings, but secondly, it's totally unclear what it would mean if you tried to assign the position to less than 5.
Consider that logically the :start and :end bound the arguments to SUBSEQ, and a valid implementation might be to actually call SUBSEQ and produce a string stream from that. So stream position 0 is string position 0, I can't any other thing that it should be.