There is a tradeoff on hardness.
I had a racing set of push rods from Crane. A brand that I never question the quality of. Hardened for use with guide plates. I ran them a few miles and then all Hell broke loose.
I was only a mile from home so I was able to limp home.
When I took it apart I found that the tips on two had broken off near the lifters and many if not all had cracked through the dimple weld that held the tips on.
Crane refunded the purchase price and I wouldn't take another set from them.
The explanation was "a bad batch of metal", but in reality they had been over hardened to the level of what a good drill bit is.
You don't use a drill bit as a drift pin because it will shatter...badly.
Anyone who works with metals will tell you that in hardening or tempering it, at some point the metal gets brittle and will shatter like tempered glass will.
So really, there is a "sweet zone" for the hardness of the metal depending on the application intended.
The fact is that in many cases it is better to have it softer and bend then too hard and shatter. It is very easy to criticize this and basically what is happening is that once you get away from OEM parts, the aftermarket is a crap shoot regardless of how well meaning the MFG is.