SK in CV’s comments are pretty much dead on in my experience, unless of course there are major problems that are uncovered during the destructive testing stage, which is usually not the case.
I am a San Diego attorney and have also been involved in several construction defect lawsuits representing both homeowners and developers/contractors over the years.
I have not heard of the law firm that contacted you, but there are a lot of firms out there that do similar mass mailing type actions. There is a ten year statute of limitations on construction defect actions, so virtually any tract development will likely go through a construction defect lawsuit at some point in the first ten years following completion. Believe me, experts can always find something wrong with construction.