Actually, starting at the top works MUCH better!! Yes, you will have to sacrifice a horizontal board, but once the top horizontal peice is removed, the rest will come off no problem, with no damage. Trying me remove the tongue from the groove on every board is a good way to truin every single board
Starting at the top, remove the uppermost complete T&G peice. Don't remove the very top piece, unless you wish to custom cut a replacement. Done it your way plenty of times (starting from the bottom) and ruined plenty of wood. Give it a shot- you'll be surprised
Use the same method for removing vertical peices- look for the double groove peice.