Semantics of shipment method filtering.

-- url of the page with the problem -- : www.ruedusansgluten.com
-- HikaShop version -- : 4

While the HikaShop-manual says that the configured plugins (I refer only to the manual type) are evaluated as if they were filters, nevertheless this implied semantics is not quite true. They seem to be applied to the shipment instance in a sequential manner.
I might as well think they are implemented using various SQL SELECTs.
In fact I get responses like this one: ITEMS_WEIGHT_TOO_SMALL_FOR_SHIPPING_METHODS = S="The cart items combined weight is too small for all the possible shipping methods" when it is not true for ALL the methods I configured but only for a subset of them.
This may be a clue to the fact that a query gets issued having a WHERE ZONE = "somewhere" clause.

I beg the authors (or anyone who knows) to disclose the exect evaluation semantics (or trivially the algorithm) of the configured shipment rules.

THNX al lot!

your timeliness, kindness and expertise are exceptional! Thank you!