When you activate legacy mode pro, everything is supposed to reset (with limited exceptions like some collections). This includes your crafting exp and leaderboard stats for the rarities, at least that is what is intended.

However, if you are crafting beforehand, you can go back to crafting and claim the items that were being crafted before you activated legacy mode (even if the rarity isn't achievable at level 1). This means you can effectively raise your crafting exp once using whatever you had previously.