C'mon. Saying that because the CF card can be inserted sideways there is a design flaw is nonsense. That's like saying that Nissan did not design my car correctly because if I drive it off a cliff it won't run any more. You can probably destroy most things by using them in ways that were not intended, much less in ways that you have been warned not to do (i.e., RTFM).
This was an accident. An unintentional mistake. But it was a mistake, and not on Canon's part, but on the user's. This does not make the user stupid, just unlucky. It just ain't Canon's fault.
I would say it's not a design flaw, per se, since I'm sure Canon is aware of the possibility of CF cards being inserted sideways. It's much more likely a design choice and it was decided that it was less expensive to go the route they chose and deal with warranty claims (whether denied or accepted) and associated loss of goodwill.