Worthy genuine parts

Once I was an user of SUBARU Legacy B4 6 cylinder 3L model, I had experienced the lecture on front transverse link rear cracked bush, just torn and destroyed, the factory engineer insisted to replace them into the original genuine parts however easily it broke, with no counter measured parts.
Judging from the concept that the axle compliance balance is established by the combination with all the parts contributing as a buffer affecting parts. Now I can realize why the engineer insisted to replace the originally certified genuine part however hard I might have been the lack of the performance.
Even a single part replacing of compliance bush into another one such as harder one means that of completely different condition in which the researching and development are not well tested and not established as in safety.
On the other hand, the finished and established condition proved by the factory researching and development is the only one to be relied on by the others. No permission is allowed to change in to any way, it is regarded as a Biblical spells.
Once a technical chief engineer said to me, "Don't make little of researching and development engineers in the manufacturer, we are making efforts continuously for making progress.".
This is why the third party parts with lacking some enough researching and developing should not be applied into your car, but the only genuine part is reliable.