There are different versions of "CAT8".
The US version of "CAT8" was ratified in autumn 2016 as ANSI/TIA-568-C.2.1.
The international standard ISO 11801-2018, with two "CAT8" versions, was published in 2018.
The 3rd edition of ISO 11801 contains 2 different "CAT8" performance classes: Class I for RJ45 connections, based on Class EA and almost identical to the American ANSI/TIA CAT8, as well as Class II, based on cabling with non-RJ45 connectors and extending Class FA to 2000 MHz.
Both Class I and Class II support Ethernet speeds up to 25 and 40GBase-T, respectively.
In addition, a TR ISO11801-9901 for cabling based on "non-RJ45" systems supporting 40GBase-T has been available since 2014. This early version of a first standard for 40GBase-T cabling was superseded by the 3rd edition of ISO11801 in 2018.
A distinction must also be made between cabling standards and test standards for cabling. Cabling testing is governed by a separate set of standards.
The TIA Standard 1152-A was ratified in autumn 2016. It specifies the parameters and accuracy required to certify structured cabling according to ANSI/TIA performance categories up to CAT8. The corresponding IEC standard 61935-1, 5th edition, was ratified in 2019. It specifies the parameters and accuracy required to certify structured cabling to ISO/IEC Performance Classes up to Class II. He also distinguishes between Class I and Class II for the accuracy of measurements up to 2000 MHz.
Both standards define how cabling based on CAT5E up to CAT8.2 components must be tested and what accuracy must be achieved in a frequency range up to 2 GHz.