If I remember correctly its a consequence of a regulation.
The -10% is probably the first reduction. I think the one with the % needs to show prior reductions. So its probably not the highest reduction the game has.
Both games have already had a similar discount, according to SteamDB.

In Europe, this is what I found:
  • Display the price of the product or service alongside the discounted price, showing the lowest price it has been for the previous 30 days.
Curiously,
  • BG3 doesn't comply to this rule, but it shows the discount correctly on the front store page (and in lists)
  • W40k:RT complies on the product page, but doesn't show the discount correctly on the front page
 
I used to just grab every free thing on EpicGS ... eventually I realized that even with infinite time there are things I would never play. Actual fishing is one thing - being in nature and all that. But this?
I'm not sure if it's something I would ever play myself, but I can see the appeal if you're into fishing and just want to relax with a casual game. At least you won't smell like fish afterwards. 🙂
 
This is a really fun tb combat game for those who enjoy this type of game
...
I remember when it was released I couldn't decide between it and WH40K: Chaos Gate. Ironically, I didn't end up getting either of them. I'll be picking up Knight's Tale soon though.