So, we have to do regular upkeep on our canvas tents (about once a year.) That includes sewing up tears or patching holes at the stress points, cleaning them so that dirt or mildew does not degrade the fibers, replacing grommets and stake loops. Admittedly, our professionally made tents require less upkeep than the ones we made, lol. But we do keep repair kits with us on all trips (waxed thread, canvas needles, extra grommets, extra canvas, the special rubber cement type stuff if you need a heavier duty patch, etc.) Sometimes a bad wind storm is all it takes to tear along a stress points. It happens.
If you read Churkina's forensic report, I believe she mentions several marks on the canvas where the knife that made the cuts to the fabric did not puncture. To me, that would indicate that, at least those parts, of the tent canvas were fairly healthy. Rotten canvas can be very brittle and if a sharp blade did not puncture the fabric... At the same time, we have to consider whether the canvas was taut at the time it was cut, or if it was slackened any (making it harder to cut,) and any other confounding variables.