Turnbuckles are usually used in control systems to apply the proper amount of tension to the cables. It is extremely important to ensure that they are properly secured from turning. The two primary ways are via safety wire or special clips. AC-43-13B explains the proper ways to secure them. This is not one of them!
If you thing that turnbuckle is bad workmanship, I’ve seen a cable fork end sleeve that is supposed to be swaged where the “builder” just center punched it several times and claimed it was “good enough”,he got really mad when I rejected it.
Wow!