There was no September US admission of Russian claims.
There is no US admission of Russian claims.
The Russian "evidence", on examination, has been shown to be bogus.
Don't forget that Russia was also a partner in the CTR, a detail they have forgotten to mention and most people would not be aware of.
Let's end it at this.
Here's what we know:
The US state has been funding biolabs in Ukraine. The Pentagon as well as Nuland have confirmed this, and this isn't an issue of debate. Nuland is on congressional record expressing concern that these labs might fall into Russian hands, which naturally begs the question: why was she so worried about that? If there were nothing in them that related to weaponization and they were just doing routine virology work etc et al, what exactly is there to worry about? Possibly IP theft, possibly something else.
Russia claims that:
During the special military operation, Russian personnel acquired over 20,000 documents, reference and analytical materials, as well as surveyed witnesses and participants of the U.S. biological programmes. The abovementioned materials confirm that the Pentagon aimed at creating elements of a biological weapon, and testing it on the population of Ukraine and other countries along the perimeter of the Russian borders.

The Russian Defence Ministry has already mentioned the names of the participants of the military and biological programmes, including those of the U.S. Democratic Party representatives, employees of the U.S. military department, and the Pentagon’s contracting organisations.

The DTRA reports have led us to the new information about key persons involved in the so-called Ukrainian projects who have been staying in the shadow until now.

Among of them are:

Karen Saylors, CEO at Labyrinth Global Health and ex-director of Metabiota's programmes in Central Africa. Since 2016, Saylors has worked in Ukraine as leading advisor at the UP-10 project, dedicated to studying ways of spreading of African swine fever.

Colleen B. Jonsson, an employee of the University of Tennessee, Director of the Institute for the Study of Host-Pathogen Systems. She observed the UP-8 project, dedicated to studying the capabilities of the Crimean-Congo fever's causative agent in Ukraine. Jonsson managed the selection of biological samples from Ukrainian personnel, provided the cooperation between the contract specifiers in the USA and the Center for Public Health of the Ministry of Health of Ukraine.

Lewis Von Thaer, President and CEO of Battelle company, a major contractor of the Pentagon and U.S. Department of Energy. Since 2003, the company has been responsible for organising research projects in Ukraine related to zoonotic infections.

Other persons involved in the Ukrainian projects are presented on the slide. The acquired materials will be submitted to the Investigative Committee for measures to bring those guilty to justice.
Now this may all well be total bullshit. But it also might not be. Whether or not you believe any of this comes down to how much you trust either Russia, or the US state. Personally my trust in either is virtually non-existent. Both are proven liars. It's possible Russia is totally blowing their findings all out of proportion. It's possible some spook agency was using these labs to test and develop weaponized pathogens. Who knows.