Thing is, it only checks the most recent. Any minor spell cast afterwards clears the prior incantem, so a different spell showing is not going to count for much. And they never actually said that they had that piece of evidence, which they certainly would have if they’d known.
We only saw it used to check the most recent spell. We don’t know that it can’t go further back, and in fact in fanfics it often can go through the recent history of the wand.
The Priori Incantatem effect of the brother wands meeting certainly seems based on Priori Incantato (though why was never explained that I could recall) and that one certainly did go back further than just the last spell.
Spells that extract the history of spells casted using a wand are canon, afaik (or was that just the most recent spell?)
I would expect they were casted on hermiones wand and the usage was confirmed.
Thing is, it only checks the most recent. Any minor spell cast afterwards clears the prior incantem, so a different spell showing is not going to count for much. And they never actually said that they had that piece of evidence, which they certainly would have if they’d known.
We only saw it used to check the most recent spell. We don’t know that it can’t go further back, and in fact in fanfics it often can go through the recent history of the wand.
But that’s not canon IIRC, which means that it should be assumed not to be the case unless EY says otherwise.
The Priori Incantatem effect of the brother wands meeting certainly seems based on Priori Incantato (though why was never explained that I could recall) and that one certainly did go back further than just the last spell.