Do we know why the flu "disappeared" during the pandemic?

The original thread is here.  The referenced document is here.  The document has been mirrored here in case of censorship.

A thread on Twitter (linked above) claims:

1. FDA admits the COVID tests weren't actually developed using SARS-CoV-2 samples, but rather uses common cold virus samples.
2. Therefore, the test is detecting the common flu.

It would certainly seem that theory explains why the flu "vanished" during the pandemic, wouldn't it?

The thread is transcribed here:

FDA document admits COVID PCR test was developed without isolated samples for test calibration, effectively admitting it’s testing something else.

A document just released by the U.S. Food and Drug Administration (FDA) openly admits that the infamous PCR test for the Wuhan coronavirus (COVID-19) was developed not with actual samples, but rather with what appears to be genetic material from a common cold virus.

In the FDA document it is stated that ordinary seasonal flu genetic material was used as the testing marker in the PCR test kits because the authorities knew that many people would test “positive” for it thus allowing them to use these results to create the COVID narrative.

It is somewhat of a lengthy read, but have a look for yourself and see the deception in plain sight. There is no legitimate test out there that accurately identifies the presence of SARS-CoV-2.

From the document:

Since no quantified virus isolates of the 2019-nCoV were available for CDC use at the time, the test was developed and this study conducted, with assays designed for detection of the 2019-nCoV RNA was tested with stocks of in vitro transcribed full length RNA (N gene; GenBank accession: MN908947.2) of known titer (RNA copies/µL) spiked into a diluent consisting of a suspension of human A549 cells and viral transport medium (VTM) to mimic clinical specimen

Another revelation in the document is the admission by the FDA that test results are “pooled” together to produce numbers that are inaccurate. The FDA is quite literally manufacturing data to support a false narrative.

So, what's the truth?

❌ The thread is incorrect.

Why?

• When it comes to PCR's limits of detection, only genetic material matters, not actual virus.
• In point of fact, you only need a small segment of the gene (specifically what the test is targeted to detect) for the test to flag positive.
• As long as the test "counts" enough of these segments to go past its limit of detection¹, it's a positive test.
• If the segment is unique to the virus you're testing for, then your positive PCR test is positive only for that virus.

If you look up what FDA chose to get that genetic material — as per the document — you'll immediately find this medical product named MN908947.2, which is in fact SARS-nCoV genetic material, with the specific segment that the test detects — rather than a common flu virus, as incorrectly claimed by the thread.

Please be cautious when sharing information.  Read, double-check, make up your own mind.  Don't give censorious assholes pretexts to feel righteous.

¹  Note on PCR cycle counts, prompted by reader comments.

By now it's well-known fact that, as the beginning of the pandemic, PCR cycle count (which amplifies the traces of detectable material with every pass) was egregiously abused by labs to make samples — that by any normal standard were neither infectious nor from actively sick patients — appear positive.

This clarification is necessary to understand a way in which otherwise-honest PCR tech can be manipulated to deceive us into believing that a disease is far more widespread and serious than it really is.