Without the original Novichok sample to compare the analysis made with a mass spectrometer, it is impossible to know if the traces found in Alexei Navalny are really Novichok. This is a huge inconsistency and it makes us doubt the veracity of the public declarations.
Although the US has been working on Novichok and similar poisonous substances since the 1970s, they quite actively deny its existence in their military arsenal.
No proof given. Until 2019, Novichok was not on the list of banned chemicals, as Russia had not confirmed its existence. Novichok was listed after the Skripals' poisoning at the initiative of the US, the Netherlands and Canada. Suspicions that the USSR had been concealing the existence of poisonous chemical substances have been raised before.
Back in 1992, the newspaper Moskovskie Novosti published an article by two Russian scientists about a powerful fourth-generation chemical weapon developed in Soviet Russia in the period of 1970-1990s.
Later, on the basis of the same article, Vil Mirzayanov, one of the authors was arrested with the accusation of revealing a state secret. In 1994, the Moscow Municipal Court tried to hold a closed hearing in the case, after which the case was returned to the prosecutor's office due to insufficient grounds for confirmation of the charges. Already living in the United States, Mirzayanov published a book in 2008 entitled State Secrets: An Insider's Chronicle of the Russian Chemical Weapons Program, in which he discussed Novichok's formula.
See an earlier disinformation example of the Kremlin accusing the US and US laboratories of developing Novichok here.