Yes, agreed. It was an accident on my part to imply that this is an instance of substandard merchandise. But indeed the "feature" should be documented.
I read your comment
And indeed I already don't trust Radio Shack when it comes to hobbist/construction type stuff -- I suspect I've unknowingly bought some manufacturer's seconds from them.
as a reference to the belief that Radio Shack sometimes sold out of spec ICs which mostly worked except when a project was more "demanding" than usual.
We came to the conclusion that the breadboard was not defective, that it was designed that way due to markings molded into the plastic.

- breadboard.png (63.16 KiB) Viewed 2068 times
I never saw the packaging; it may have been documented as being that way.