It's working here with your configuration:

I just ran docker build . --platform linux/amd64 I got an image on my ARM Mac.

docker image list
REPOSITORY   TAG.      IMAGE ID       CREATED         SIZE
<none>       <none>    8394447e8084   4 minutes ago   59.6MB

syft scan 8394447e8084 --scope all-layers
 ✔ Loaded image 8394447e8084
 ✔ Parsed image sha256:8394447e80846d52d7047063a7b5c47ff2a1795e5baeda03d3fb6362a99f9f94
 ✔ Cataloged contents 655512525c2ef2fe56e4890d9acd5852ea5729901fb1a99abcccd88c6bccae60
   ├── ✔ Packages                        [4 packages]
   ├── ✔ File digests                    [943 files]
   ├── ✔ File metadata                   [943 locations]
   └── ✔ Executables                     [2 executables]
NAME        VERSION          TYPE
base-files  12.4+deb12u10    deb
netbase     6.4              deb
redis       7.4.2            binary
tzdata      2025a-0+deb12u1  deb

Are you using an old version of Syft? The latest is v1.21.0.
Do you have a syft configuration file that is overriding the defaults? (I am not)