I suppose the intent of foiled items isn't to just signify a special item, but a special league-specific item?
Because the idea OP had was that since loreweave can be elder/shaper due to the inputs, loreweave should be able to be foil too. It depends on GGG's design philosophy regarding foils.
This series of reliquary items is league specific items. Having the craftable league specific items (like The Taming) still available "in foil" works, not so items outside the series (like Loreweave).
However, in the future there may be other reliquary sets that may make other items available.