Thanks. If it was just the fish and the tuna, it's easily avoidable, but I am very curious to know what the other things are
There are many, many issues. How separate dairy/ meat and sometimes fish kitchens are apart from each other. Which suppliers establishment gets their supplies from. (Mehudar establishments have more restrictions where to buy their material from.) Onions and eggs overnight. Who has access to the kitchen. No mashgiach temidi or even working mashgiach. How well vegies are cleaned. The list goes on.
According to the Vaad, only what they list as "extra hidurim" meets the same standards as KCL Lakewood, or Kehila Kashrus Brooklyn.
Those are usually considered standard middle level hashgochos.
Nirtbater, Volover, Eidah, Rubin, and the like have extra stringencies. (Small but major example: in chicken if they check for tzumas hagidin. If they let liver be kashered after 3 days when frozen)
The Vaaad says "You should be aware that all the vendors who received all of the checks have sacrificed financial expense and culinary expertise to achieve this" to be labeled as mehudar. So there must be many differences.