"There is no other, clearer, later connection between Finno-Ugric and Proto-Indo-Iranian speakers." (link) This claim seems unfounded, as there seems to be contacts between Seima-Turbino and Sintasha, p. 134-136 Social Complexity in Prehistoric Eurasia.
https://indo-european.eu/2018/05/consqu ... an-region/
Seima-Turbino phenomenon refers to a pattern of burial sites dating from 2100 BCE to 1900 BCE found across northern Eurasia, from Finland to Mongolia, which has suggested a common point of cultural origin, advanced metal working technology, and unexplained rapid migration. The buried were nomadic warriors and metal-workers, travelling on horseback or two-wheeled chariots. The name derives from the Seima (Sejma) cemetery at the confluence of the Oka River and Volga River, first excavated around 1914, and the Turbino cemetery in Perm, first excavated in 1924.
These cultures are noted for being nomadic forest and steppe societies with metal working, sometimes without having first developed agricultural methods. The development of this metalworking ability appears to have taken place quite quickly.
The Altai Mountains in what is now southern Russia and central Mongolia have been identified as the point of origin of the cultural enigma of Seima-Turbino Phenomenon.
The earliest possible date so far for the end of Proto-Indo-Iranian as a linguistic unity is 2000 BCE and the latest possible period of Indo-Iranian linguistic unity is the 18th century BCE. p. 10, Linguistic supplement to Damgaard et al. 2018: Early Indo-European languages,
Anatolian, Tocharian and Indo-Iranian