Yep - At the time I think this inaccurate bit of folklore fitted well with the Withnail theme of 'endings', it well befitted the film's vibe for people to believe that it was his tragic swansong. And I suppose blues is all the better for it's mythology.
Or this - for Withnail & I fans... he was said to have been killed days after but I heard that was apocryphal, there you go.
https://www.youtube.com/watch?v=FI8d36w_ijw