While that might be an overreaction -- to be clear, it's the "they never used the icons" part that is the main problem here.
For designers or artists of any kind, the general accepted pratice is that you're allowed to display/use pubicly released (even if sold e.g. in a book, TV show, etc.) work you've created for others for purposes of a portfolio, or that you've been given permission to. It's a kind of fair use.
On the other hand, if the material was never released, you don't EVER show it unless you have permission. Because that leaks potential future ideas, different directions that are inconsistent with their branding/image that they don't want public, "mistakes" they made, etc.
You absolutely should NEVER post stuff to a personal website you did for work that was never publicly released, unless you have explicit permission.
For designers or artists of any kind, the general accepted pratice is that you're allowed to display/use pubicly released (even if sold e.g. in a book, TV show, etc.) work you've created for others for purposes of a portfolio, or that you've been given permission to. It's a kind of fair use.
On the other hand, if the material was never released, you don't EVER show it unless you have permission. Because that leaks potential future ideas, different directions that are inconsistent with their branding/image that they don't want public, "mistakes" they made, etc.
You absolutely should NEVER post stuff to a personal website you did for work that was never publicly released, unless you have explicit permission.