I take issue with the way you're labeling some hechsherim as "mediocre", but otherwise this is correct.
Whether or not this is the only interpretation of Reb Moshe's psak, let me just say that this is a VERY unconventional approach towards kashrus and certainly isn't something that is being followed by any serious kashrus expert. To whoever in the kashrus field you're listening, I particularly heard that numerous times from Rav Elephant, one should do utmost due diligence when it comes to hechsherim. Many do have subpar standards which most would not rely on. Many simply don't have the knowledge/capability/manpower to run an effective operation regardless as well intended they might be. Chezkas Kashrus doesn't mean that every well intended yid who wouldn't knowingly serve tarfus is somehow magically transformed into a kashrus mumcha in today's extremely complicated kashrus field.
Of course, this doesn't warrant spreading unsubstantiated rumors based on fuzzy evidence and imaginary facts, but you have been pretty vocal here with your unconditional chezkas kashrus mehalech. I believe that a disclaimer is in order that this is all based on a very unique attitude towards kashrus you personally follow, which isn't endorsed by any serious kashrus expert today.
Regarding timtum halev, as others have pointed out, this is also not a position most would agree to.