The mount program does not read the /etc/fstab file if device (or LABEL/UUID) and dir are specified. For example:
mount /dev/foo /dir
If you want to override mount options from /etc/fstab you have to use:
mount device|dir -o <options>
and then the mount options from command line will be appended to the list of options from /etc/fstab. The usual behaviour is that the last option wins if there is more duplicated options.