Can you explain why mount -o ro,noload sometimes modifies the filesystem?

This reddit post explains that using mount -o ro over NTFS changes the atime of files. They say something like that the kernel is not obliged to honour the ro flag, and to achieve reliable readonly one must mount the device as readonly block device. I'm very confused by this seemingly buggy implementation! For various filesystems: which method is reliable, in which cases, and why does the standard mount -o ro,noload not always work reliably! And by the way why does mount have the weird syntax mount -o ro rather than a more natural syntax like mount --ro? - "mount -o ro" does not write-protect last access dates on NTFS.