From my shortcuts.vdf file, Halo Infinite has the appid C0 83 BF F8 which in python when read is displayed as the following.
`

print(d["shortcuts"]["103"]["appid"])
-121666624
`

Steam uses the appid for grid images. It seems like the byte data is being read as uint32 instead of int32 by steam. The same thing happens with all shortcuts ids I've checked.
`

print(d["shortcuts"]["103"]["icon"])
C:\Program Files (x86)\Steam\userdata\XYZ\config\grid\4173300672_icon.ico
`