After it happened to me I began looking into it. DFDR revealed a rapid change in the wind at a very late stage in the landing which I countered with a very positive flare. The touchdown was firm (but not heavy) and the synthetic "Pitch Pitch" call was heard. I didn't think that I'd overdone it on the pitch and so I got in touch with one of our engineers who was kind enough to email me the documents for our new jets and that's where I got the figure from. Quite possible that the number is different for older jets and possible that it's programmeable too. I can try and get you the document reference if you want?