To prevent Turkey getting engines from Ukraine I suppose. That why Pakistan would be forced to buy Z-10 from China instead of buy T129 from Turkey.
In fact, If I'm not mistaken, the US offered helicopters before China. However, Pakistan prioritized Chinese and Turkish companies.
I do not think there is such a problem for China. The Turkish defense industry is not a threat to China's defense exports. In essence, Turks pose a threat to the market share of some of the traditional suppliers such as USA and France which mostly in NATO standard logistics infrastructures. Helicopter sales to the Philippines or the growing supply role in countries such as Indonesia and Malaysia are an example.
On the other hand, made a series of intergovernmental agreements between Ukraine and Turkey, and this process was followed by some joint venture companies.
Among these companies, there are also engine specialized ones. Zorya-Mashproekt partnership under the name Lodos Propulsion is one of them. As you know, Ukraine bought 4 Milgem corvettes and wants Zorya-Mashproekt turbines on these ships. Starting with the Ukrainian corvettes, the Turkish ship industry will have solved the alternative turbine propulsion source. President of Ukraine Zelenskyy announced that not only corvette but also joint UAV and air defense systems will be developed. There is already collaboration in many subsystems, especially for land systems that have been going on for a long time. Collaboration on propulsion solutions is one of the most important topics in these strategic perspectives. In this context, Turkey is also interested in some Ivchenko-progress projects. Preparations continue to establish a joint venture with this company in 2021. Ivchenko will likely become the main engine partner of Turkish unmanned aerial vehicles, together with TEI. In some special cases, Ivchenko's role will be valuable when considering TEI's GE partnership and especially its work share in US aviation companies.
In summary, the fact that one of NATO's most important military resources is rapidly leaving the US logistics and starting to rival this country in foreign markets is not a development that China would like to prevent. On the other hand, strategic cooperation between Ukraine and Turkey is not a matter of a few years and is conducted within the level of presidents.