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I chose not to tick "Remember this location" and this could explain why my subsequent searches weren't locked to the postcode I typed (not my physical location). Anyway, the SERP looked almost identical to the default, so I am not sure what to expect. Perhaps the test is to see how many people use the option?
Behavior is not consistent on single or multiple words, or on singulars and plurals, btw. Also to take the liberty of using specific examples, [hardware] doesn't return the location input field, nor does [hardware store] singular... but [hardware stores] plural does return the prompt and the input field (which then leads to map results).