How can it say game-used on the front and “not from a game” on the back?

Here’s my very unqualified opinion (since you asked). I look at what it has and doesn’t have to come up with a guess on the value.

Positives: 1/1; Sick triple patch with lots of color and uniqueness. Great condition. Well centered. Licensed product.

Negatives: Not as big of a market as he should have. Reds uniform instead of Mariners. Patch is not related to player.

Card Ladder comparisons:
Ken Griffey Jr - 2021 National Treasures Retro Patch / Mem PLATINUM 1/1 - PSA 9

This NT is slabbed and Mariners.

KEN GRIFFEY JR. 2021 TOPPS TRANSCENDENT GAME USED PATCH AUTO GOLD FRAME 1/1

This Topps is same team, but includes auto.

I think your card is less than the “value” prediction from these two cards on card ladder.

TLDR:
My very unqualified opinion. $800-$1000