The term “rot” was used in Ralph Mayer’s Artist Handbook. I think this may be better described as not ideal, or less suitable for a stable surface. But you can find many examples of how the canvas can change the look of the painting over time and effect adhesion. Check out J.E Russel’s exhaustive analysis in “A Study of the Materials and Techniques of Francis Bacon (1909-1992)” Go to page 204. She states: Paint is applied directly to raw canvas in Bacon‟s work, with the results that the oil medium is absorbed to some extent, leaving the paint underbound. She also mentions later color changes in the Article: “The sinking of oil into unprimed canvas can lead to increased acidity and darkening, and halos of oil staining where raw canvas is exposed.” Check out the full 550 page document here: https://core.ac.uk/download/pdf/4148915.pdf