I have no idea what standing should be given to this "anecdote".
What interests me is that it seems to indicate that bloodstained people could traverse Whitechapel and attract minimal attention. This character (if he existed) seems to have had no qualms - other than hastening - through an area which was supposedly in the grip of terror. He does not appear to have been stopped, or to have been acting in any way furtively.
Which is why I tend to the view that he was probably an invention - nothing further seems to have come of it.
It throws a gloss on whether or not "Jack" would have had to have acted in any particular way, or have attracted attention, in moving between Mitre Square and Goulston St after Eddowes' lkilling.
I think that's a slightly different issue. It was dark, there were other people around, and I suspect it depended on how he moved around as much as anything else. If he wasn't acting suspiciously (unlike the bloodstained, parcel-carrying Mitre Square dasher) he could easily have been seen, and not noticed.
I suppose that, in an area full of butcher's shops, where they slaughtered the beasts on the premises the sight of a blood-stained man would not have been all that unusual. If (& I accept it's highly questionable) this is a sighting of the killer it probably poses more questions than it answers, because it would mean that a murderer who fled north-east after killing Eddowes, travelled in the opposite direction after killing Kelly. Many thanks to all for your observations on this, by the way.