Seems to have a Shotgun theme, plus very important core rewards happening right on the tail end of Save the World finally being integrated into the BR Lobby after the BR XP announcement. Balanced with 0 V-Bucks being as all the other rewards are hefty.
Seems like thought was put into it to please players who don't own everything yet. My perspective is as a player since September 2017.
Otherwise, I was under the impression it was always purely randomized, but this looks as if created by design:
Shrapnel Headhunter = Shotgun Dmg+50%
Helium Shotgun, Super Shredder,& Room Sweeper
2x Legendary Survivors (1x Ventures, 1x Twine)
Legendary Traps: Sound Wall, Floor Freeze, Wall Darts, Wall Spikes
P.S. – I'm a tin foil hat wearing person that believe Save the World has been shadowed away by design due to its leperous business/financial situation between too many free V-Bucks to original players, Loot Llama Class Action Lawsuit, and much more very concerning financial short falls that would have ended literally almost ANY other game.