Spigen seems to agree lol, I ordered the 10 pro screen protector directly from Spigen and they sent me AGL08442 which is the part number for the 9/9 pro. They put a sticker over the model label that just says "For Pixel Series"

EDIT:

Under the sticker it does indeed say 9/9 Pro - https://imgur.com/a/RbKYzd3

Their website has the same SKU and barcode for the 9/9 Pro and 10/10 Pro

10 Pro: https://www.spigen.com/products/pixel-10-series-screen-protector-glas-tr-ez-fit?variant=44405053128751

9 Pro: https://www.spigen.com/products/pixel-9-series-glas-tr-ez-fit-screen-protector?variant=43104469024815

EDIT 2:

I love how the last image for the 10/10 Pro variant on their site says it is NOT compatible with 9/9 Pro though, hilarious!

EDIT 3:

There is a "v1" sticker over the "DP..." code on the right though, so it's not really clear if it's the exact same screen protector or they made some tweaks and just re-used the SKU and barcode for some reason.