The non-holo Common cards within the Unbroken Bonds booster packs within the Pre-release kits, can have a small chance of being glossy. I don’t think any of the pre-selected cards within the kit will ever be glossy.
FWIW, when I’ve first heard about this, I bought three of these pre-release kits from three different sellers. Three out of four booster packs in just one of those kits contained the non-holo glossy cards (luckily including the Pikachu I wanted 
And I’ve just checked, but I don’t have the glossy Growlithe nor Porygon, sorry. 
) All the other booster packs were just regular ones.
And tbh, I would consider them as repeating errors, rather than an actual variation to collect. More like a nice-to-have. Mostly because a lot of modern cards can have this same glossy cardstock. I’ve seen glossy cards on:
- Unbroken Bonds non-holo Commons
- Shining Legends non-holo Uncommons
- Pikachu Libre deck cards
- Unified Minds non-holo Commons
- Hidden Fates shiny Pokémon (both glossy and textured variants, on top of regular ones)
- XY Evolutions (don’t have a picture for these) - I would love to get my hands on a glossy base set reprint Pikachu
- French Temporal Forces RHs
- etc.
Seems like it’s just a print variation that can happen sometimes.
Greetz,
Quuador