So, I got it running and can confirm your observation. After first tests I think that the issue comes from Seed Arduino FS ff.c.
If I let it run on PlatformIO, use the debugger and set a breakpoint in the line:
if (!obj || !obj->fs || !obj->fs->fs_type || obj->fs->id != obj->id || (disk_status(obj->fs->drv) & STA_NOINIT)) {
and continue after it reaches this line the files are listed
Edit: No, I spoke too early. It doesn’t work. The program complains that: Dir is opened, Perhaps it must be closed after the first access.