This whole tier discussion is almost non-existent in the US, it's not about different standards in different places. The overwhelming majority of people eat from a huge list of hechsherim in the US, FWIU that is not the case in EY.
Is this really true?
I mean, my knowledge of flatbush kashrus is over a decade old, but from what I remember, there were plenty of people who would not eat from every one of the "accepted" local flatbush hechsherim. Only ate from Rav Gornish, or him and Kehila Kashrus, or only the VHROF ect... (Don't attack me on specifics, it been a long time...)
Every "chasiddishe" "heimishe" hechsher is the same? REALLY?
In EY, It's probably fair to say that the far majority of (Black hat, streimel...use whatever word you want) will eat from each one of the big 4 plus much of the second tier (excluding what is obviously communal politics) plus whatever is their local hechsher (if there happens to be one, if there are two, just from one
)