the note is a friendly warning. If you have read the description of the WP bit then you have seen the last and by my opinion critical sentence which says you that there is no place for mistake:
Write Protect— This bit enables write protection to be used for all write-protectable registers. While clear, WP allows write-protected registers to be written. When set, WP prevents any further writes to write-protected registers. Once set, WP can be cleared only by reset.