Deborah Tannen has a book entitled, "Conversational style". She studied (sort of) "under" Grice at UC/Berkeley, and her book is an analysis of a tape recording over Thanksgiving! She noted that HER conversational style varied from others's!
Helm was quoting some conversation between Ferrari and Borges where Borges poses a hypothesis: that Spaniards use interjections and exclamations and thus that their conversational style varies from, say, his own!
Grice possibly had something like that in mind. Only he wouldn't say it!
Years later, Elinor Ochs went to Madagascar and noted that all of Grice's maxims were violated. She published her results in a journal of pragmatics, under the provocative title of the alleged universality of conversational implicature. In Madagascar, the use of "a woman" may NOT implicate "not my wife", since Madagascar utterers are reluctant to provide as much information as Grice desired!
In Pears' Encyclopedia there is an entry on innuendo or understatement, and they note that this is a British thing, but I wonder. Grice came from an affluent family in the Heart of England, and his conversational style was possibly moulded there. But his maxims (and 'desiderata' as he called them in earlier lectures) were meant to provoke Strawson, who came from a similar socio-economic background.
Amusingly, Grice went to Harvard and started to turn his terminology "Kantian": 'maxim', 'principle', etc. This leads to a sense of 'universality'. But Hegel noted that while Kant's reason MAY be universal, this reason has 'cunnings', by which he meant the realisations of this universal reason in _history_, and nobody could beat Hegel in the philosophy of history.