That is interesting. Some on line pictures and descriptions, including RHS, show or describe slender spires or upright spikes. Others show fasciated blooms like yours. It looks as if there's quite a bit of variability. Did you grow yours from seed?

Yes, I noted that as well when first googling the plant that for every site that shows 'Purple Explosion' as fasciated , others display it something a bit different, possibly varietal mix up. I acquired it as dormant root stock a good few years and in subsequent years a few seedlings of a bit different form and color have appeared, though many with leaf spot issues.

Unique looking!

Ive observed fastigation i a few veronicas;

Sunny Border Blue frequently has”divided” blossoms, Red Fox and Vernicastrom is notable for its varied ( i think ugly) flower forms