Worst case tolerance occurrence in L6564 IC

Hi,
On page 11 of L6564 datasheet is paramerter V(ZCDT) ("triggering voltage")
Do you know how likely the 0.5v or 0.9v parts would be to occur in any batch?

L6564 datasheet
https://www.st.com/resource/en/datasheet/l6564.pdf

There is no good way to know.
"occur in any batch?" With the same date code, it is likely they are close together. There is no guarantee of that.
Somewhere in the ST-factory there is an engineer that knows because his job is to watch all numbers. But you will never find him. Even if you could find him, some time down the road ST will have a strange batch of silicon or they will change the process and you will have a problem.
This is the difference of "hobby" building and "production" building. To make a good manufacturable product you need to design so that 0.5 through 0.9 work the same. If you don't, some time maybe years later the product will stop working (in production).

That's why industrial design is based on minimum specs for all chosen components in said design. That way long term stability and reliability is ensured.