While there is a chance that they may reassign the seat, there's a much greater chance that they will not.
Any changes though once you lose status to a seat you are no longer entitled to will be charged as you found out.
The last line is probably worded wrong, as obviously you can RESERVE any seat you want if you have status for that seat. But of course, if you lose your status, you also run the risk of losing your seat if they do a swap or something.