Neinda, are you sure you are remembering that correctly? The item level of any tracery is the item level of the slot into which it is placed. Any time an enhancement rune is applied to a slot, the item level of that slot increases. Any time the LI is reforged at one of the "break points" (see the table in the section "Tracery Advancement and Item Levels" on https://lotro-wiki.com/index.php/Legendary_Item), the item level of that slot increases – by a lot! There is no need to unslot the traceries or put in traceries with a higher min/max level in order to benefit from item level increase of a tracery slot.
It is not at all obvious, even to someone who reads the wiki let alone other guides which tend to not mention this at all, that the tracery slot item level gets a big boost at various "break points" simply from reforging. As someone else mentioned, go ahead and use whatever enhancement runes fall into your lap but don't spend any Ancient Script to buy them until you are past the final "break point" because any enhancement runes used before that will be superseded by the first reforge you do upon hitting the next level "break point".
Going from 130 to 140 is a one time good deal that we can use this feature in the system as there is no difference in the traceries between 130 and 140. It won't work the same with other levels but will for the 130 to 140 window. I know several people who used this particular method to upgrade weapons and avoid using script or dailies to get enhancement runes. Make sure you get a scroll to remove the old traceries. Put on the least expensive new ones that you can find to raise the level of the slot (not the max level but the actual level) then overwrite them with the old good traceries. You save the difference in enhancement runes from the 130 weapon to the base 140 weapon. Anything that saves a bit of grinding and repetitive dailies is a positive.