Moreover, this long sword Spiritual Treasure doesn't offer any enhancements to Magic Practitioners.
Spiritual Treasures suitable for Magic Practitioners are those that can provide them with enhancements.
For instance, increasing Spell power, reducing the consumption of Spiritual Energy during Spellcasting, extending the range of Spells, or even... ignoring the silent incantation of Spell hearts.
For a relatively basic Foundation Establishment Spell like the "Thunder Summoning Technique," there's no need for silent incantation; it's an instant cast, but some more complex Spells with greater power do require silent incantation of the Spell's heart.
Some even more powerful Spells need the caster to form hand seals to cast them.
In such complicated situations, having a Spiritual Treasure that can ignore silent incantations is naturally a significant enhancement for Magic Practitioners.
However...