"to say ALL low number Springfields are unsafe is a broadly incorrect statement."
Functionally, though, it is a correct statement.
There is no way of knowing how many low-number receives are bad, nor is there any truly adequate method of testing the receiver that will provide 100% surety.
Let me give you an analogy...
Say I were to place before you a box 100 rounds of .357 Magnum ammunition.
I tell you that, of those 100 rounds, I might have accidentally loaded some of them with C4 instead of WW 296, but at the same time, I might have pulled all of the bad ones, so some of them definitely are OK.
You might fire 100 rounds without a problem.
Or, you might also, on the first trigger pull, put a chunk of recoil shield through the back of your skull.
You really want to play the odds?
Presented with a situation like that, the only possible conclusion that can be drawn is that ALL of the cartridges are unsafe, and all of them should be treated as such.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.