Forced heirs are any child over the age of 23 or with permanent disability regardless of age. A forced heir can also be a child with an inherited condition that may make them disabled one day. This is all a nightmare for estate planners (Thank you, Legislature).
Usually when we refer to a forced heir in a will, we are only talking about a contingency. That is, IF I have a forced heir, then such and such happens.
People do not normally assign the status of forced heir to their children. They are either forced heirs by operation of law or they are not.
So, it would depend entirely on the exact wording of the Will. If the will says “I leave the forced portion” to any of my children, then that child would not receive anything by virtue of that bequest because, in fact, they are not a forced heir.