I would like to clarify the secrecy part.
When designers make a new design, it is with the intent of creating a winning airplane. They protect their advantage that they have spent many hours (many hundreds of hours) drawing, drafting, and creating.
If the airplane will go into production, then there are royalties to gain (these are very small amounts per airframe and perhaps if enough copies are sold it may help defray the costs of a couple of nice dinners), but those royalties are only payed to the designer by the company licensed by the designer to produce the airplane. Why, then, is it kept secret. Well, the tooling needed to go into production of a new F3A airplane with unique parts can cost up to $20,000.00 (thought they were really cheap to make and the manufacturers just want to get rich, did'nt you). It takes about two to three years to break even on that design, and then you have to hope that you can sell a few more to make a little cash to pay the rent. Hopefully, you can do that before the design is pirated and unauthorized copies are produced in China and sold as an ARF with no royalties to the designer.
As far as the company releasing the design, it is not the company's choice. The designer authorizes if and when and what can be released. Guess what. If the designer cancelles the project and says no, it will not be produced, then it does not get produced, at least not if the company ever wants to get another design from the same person again.
Recently, one company had an unauthorized release of one of it's designs. That company's new design production was due to start in late April, but a Chinese ARF maker has already produced several thousand for a Western based company that took the pictures and produce it as it's own design. To make matters worse, the Chinese ARF has had incredible structural failures, and this could have an adverse effect on the original when it is released.
Mark