What he is trying to say is that every time you change your weapon appearance you are forced to use the new one but unable to retain the old one, or even its original look.
So for instance, I have a Velcoffer staff that I previously used the Ivory Queen skin on. 2 months later I used the Bunny one, and now to get along with the festive season, I wanted to use the new Broom Stick look on the same staff. I end up losing the original Velcoffer staff look, and also losing my Ivory Queen skin as well as the bunny one just to join in for the festive season. This is dumb because once we lose it, we lose it forever. (Plus you can not use Velcoffer as skin itself so if you changed the appearance for a Velcoffer weapon, you lose it forever.)
It would have been way better if players are free to choose whichever looks (TP or not) was used on that very same weapon at any time, just like how you can switch between titles (above your names) and not forced to use the title that you received at the latest. Weapon bound is fine.