Necromancer and engineer starting headpiece
I haven’t tried this recently but are they actually soulbound? I noticed in the past that the item sometimes says soulbound when you do that but is actually account bound and another toon can take it out of inventory and use it.
Just tried it using 1 basic stone, the starter boots and level 1 boots purchased from an armorsmith, selecting the stats of the level 1 boots and the appearance of the starter boots (as you would do for the mask). The result was an account bound pair of boots (that I could equip on another character).
So it still works, and it still shows the message that the transmuted item will become soulbound.