Yixing Company sells spacecraft to the outside world, just like a technology manufacturing company sells computers.
Of course, a spacecraft is not as simple as a computer, but the situation is largely the same. Some companies sell computers around the world, and they certainly don't have to worry about other companies cracking the secrets of computer manufacturing.
The technology of spacecraft is fundamentally uncrackable. Without sufficient theoretical support, the arrangement of internal light beams in the anti-gravity system is so complex that it's completely incomprehensible, making imitation almost impossible.
Therefore, selling spacecraft does not involve issues of technological confidentiality.
Additionally, the main core and hull of modern spacecraft often use compressed materials. It would be impossible for imitators to purchase the relevant compressed materials used in manufacturing due to costs.