How about because (for example) the OU certifies fish without simonim and without a mashgiach temidi, something that Rav Belski decried as wrong?
I have no idea but that is not what your comment was about. You were discussing מעשה השחיטה and responded that chassidishe hechsherim look for things like mikveh, dress code, and shaving. You wrote also that it would be an
extremely long stretch to think that anyone that really cares about Glatt Kosher meat would rely on the OU for that
To me, saying that it's pretty much impossible for someone who cares about Glatt Kosher to rely on OU for the reasons you supplied is wild. That said, I think you agree, but at the same time have a somewhat similar mentality, hence that statement.