By the way do you remember your tire sidewall bulge, I just noticed one on my front tire so I ordered a new front set to be on the safe side and asked the proprietor of the tire biz what he thought about it, he said I could of driven like that for a very long time and said many drive all the tire's lifespan. It would only cause problems if you hit a pothole in the very same spot.I kept both as spare because sometime these sizes are unavailable for 6 months or more. I'm going to order rear ones too as spares for next year, a supplier ordered too many and are giving a $100 discount on each.
Mine was a bit worse than yours and I got it replaced rather quickly. I think tires are the only wear item I never take chances with, especially on a car like this. The thing about a bulge is, it might not get worse or it might. There is always a risk it could burst. If people can win the lottery or land on a single roulette number, there is always a chance that a pothole or something else hits that exact weak spot.
Let's say that
20 inches =~ 50.8 cm.
Circumference of the tire = pi x 50.8 cm =~ 159.5 cm
Chances = 3 / 159.5 cm = 0.0188 or 1.88%.
So with a 20 inches tire and a sidewall bulge of about 3 cm, the chances that a pothole can hit the same pot is around 1.88%.
But in reality, only 25% of the sidewall is exposed to potholes, which is outer 25% of the arc, which means that the exposed section is about 40 cm (25% x 159.5 cm). That certainly increases the chance to 7.5% calculated from 3 cm / 40 cm.
In summary, mathematically, the chance of potholes hitting the same spot is 1.88% (1 in 53 pothole hits). But on real life application, the chance of potholes hitting the same sidewall spot is 7.5% (1 in 13 pothole hits). Pretty high chances.
But not all roads have potholes, which means we have to go through full chain of probabilities. For country like Canada with average 1-2 pothole every 10 km, the chance is still very high which is 1.875% chance every 10 km or 1 in 53 pothole hits. You roll the dice every 10 km. It's scary chances.