something that isn’t an SD card to the /sdcard directory?
Could be.
On my phone (Poco X3 Pro - stock Android 11, MIUI 12) the /sdcard is a symlink pointing to /storage/self/primary which itself is a symlink pointing to /storage/emulated/0, which is /data/media, the user-accessible portion of internal storage.
Though from what I can find it anyway is just emulated FAT filesystem which is actually ext4 under that.
Something about backwards compatibility as the directory used to actually be used for SD cards in the past.