When I mentioned "non-linear" I was referring to the (bad!) habit of people tending to compare HS30-prefixed production serial numbers and dates with HLS30-prefixed production serial numbers and dates. There is a tendency to think of the factory as a sausage machine that could not be turned off and on, and that - therefore - HS30-00xxx must have come off the production line on the same day as HLS30-00xxx. That's not what happened. Sequential body serial numbers were assigned in a linear fashion for each prefix ('S30', 'PS30', 'HS30', HLS30' etc), so 'S30-00123', 'PS30-00123', 'HS30-00123' and 'HLS30-00123' would all have been made, but not necessarily within the same time period as each other.
I'd urge GREAT caution in assigning too much trust to stuff written on local documentation after import. For example, one of my cars - a 1970 Fairlady Z-L - has been assigned as a '1982 Fairlady Turbo' by our UK national vehicle licensing agency. I now have a government agency document which says so, so it must be true, right? Well, no...