Can UA Lore Mastery's Spell Secrets feature change the damage type of a spell that does not deal damage immediately?

Question

For UA Lore Mastery, Spell Secrets states the following:

At 2nd level, when you cast a spell with a spell slot and the spell deals acid, cold, fire, force, lightning, necrotic, radiant, or thunder damage, you can substitute that damage type with one other type from that list (you can change only one damage type per casting of a spell). You replace one energy type for another by altering the spell's formula as you cast it.

This applies easily enough for instant-damage spells. However, the wording does not specify that the damage must be dealt immediately in order to be eligible for the change. Would I then be able to change the damage type of, say, holy weapon from radiant to another type? Or substitute the necrotic damage of a symbol spell for cold?

Note: I am aware that Lore Mastery is playtest material.

Answer 1

There are no hidden rules

1. Is it a spell?
2. Does it do acid, cold, fire, force, lightning, necrotic, radiant, or thunder damage?

If the answer to both is yes then you can use Spell Mastery.