You are very unfair and I totally disagree.typicall for sigma.
you wonder if they have a quality management at all.
how can such an issue not be noticed and fixed when developing a lens?
This is NOT a Sigma problem.
It is a Canon problem.
Canon's business is too sell Canon products, not Sigma or Tamron or any other brands.
When Sigma sells 1 lens, Canon does not receive any yen/dollar for that. Why should they care about them? Sigma should already feel happy that Canon doesn't try to definitely inactivate their reverse tech and making their products unusable --> end of business.
Does that then mean that you should buy Canon tripods, Canon monopods, Canon camera bags, etc?
Where do you draw the line?
Canon need to realise that it is the ecosystem around their products that keeps them alive.