Richard,
While I appreciate your lengthy response (on previous thread) I do want to make a few observations.
I would really caution about telling people they can enter under visa waiver to do time building or conversion. These are completely up to interpretation by the Adjudication officer at port of entry and its entirely possible that they do not understand the time building concept or even conversion process(where you could actually receive training) and sent the pilot back to their country of origin.
The Visa waiver is considered a visa and falls under the same statue/jurisdiction as the B visas (both Vacation / Business). The J-1 Visa CAN NOT be converted to in the US and requires you to leave the country and pending who you are talking to may require you to make the application from your home country (where your passport was issued/from).
Another issue is that having a visa in your passport does not mean you will be allowed to enter as the final authority is the officer at the port of entry. Generally speaking EVERY student wanting to receive flight training towards a license in the US should get a visa - even if you are doing it while on vacation. Of course if you are sunbathing in Florida and feel like going for an introductory flight you will not need a visa but if you are planning to get training toward a license/rating you should consider this before you come to the states.
One last observation...The school is NOT responsible to ensure your legal immigration status which is why some schools can say don't worry you don't need one...Think about it...