I agree but in the context of the article, I believe the classes being sealed aren't meant to be overridden.
If the author has spent time optimising to that level, overriding probably isn't necessary or warranted in that area.
If the author has spent time optimising to that level, overriding probably isn't necessary or warranted in that area.
Classes should be designed for extension on purpose, not as oversight, one of the SOLID pillars.
Taking advantage of an oversight is an open door for fragile base class problems and hard to track down bugs.