Read the strace, not the man page.

Linux is taught as a list of commands, which is why people who have used it for a decade still cannot say what fork gives the child, why their container takes ten seconds to stop, or what D state means. The commands are the interface. The contract is underneath, and the contract is what breaks.

int fd = open("/var/log/app.log", O_RDONLY);
if (fork() == 0) { read(fd, buf, 4096); _exit(0); }
 
openat(AT_FDCWD, "/var/log/app.log", O_RDONLY) = 3
clone(flags=CLONE_CHILD_CLEARTID|SIGCHLD)       = 4127
[pid 4127] read(3, "...", 4096)                 = 4096
[pid 4126] lseek(3, 0, SEEK_CUR)                = 4096

The parent never read a byte and its offset is four kilobytes in. The defect is not in the syntax — it is in the fact that a descriptor table, an open file description and an inode are three different things, and fork copies only the first of them. None of that is visible without a model of the kernel underneath. So there is one here.