I'm probably in the minority, but pulling out Regular/Poke/Master reverses for a set that will mostly be catch-up starter deck cards just seems sloppy and unappealing to me.
151 had that iconic lineup of original Pokemon. The Poke/Master reverse holos work because the set has a highly collectible, clear theme. It makes sense, is popular, and looks good in a binder.
Terastal Festival is a "best of" just like every other high class set. Most of the Poke/Master reverses are somewhat competitive, and a few are highly collectible (the eeveelutions). A celebratory set that I'd say earns its indulgent holo treatment.
But with Prismatic... aside from the eeveelutions, why go all in with three reverses for a set that's mostly just bulk starter deck extras? Thematically, what's the occasion? Is the main set so slick and worthwhile that it seemed appropriate to polish it up with extra holo designs, like 151 and Terastal? Or are we just doing this because master balls and eevees made a lot of money in Japan.
Maybe I'm just being a stick in the mud. And I'm sure this set will be very successful either way