As far as I know there are no ISO standards for motion picture film speed, except for non-professional colour reversal camera films, that are treated in ISO 2240 (Photography — Colour reversal camera films — Determination of ISO speed), which in the 'scope' section says: 'It also applies to 8 mm and 16 mm motion-picture films used in non-professional applications. This International Standard is not applicable to professional motion-picture films regardless of their applications'.
The standard for determining film speed for colour negative film is ISO 5800 (Photography — Colour negative films for still photography — Determination of ISO speed), which in the 'scope' section says: 'does not apply to colour negative films for motion-picture and aerial photography or for making intermediate negatives', and for black-and-white negative films is ISO 6 (Photography — Black-and-white pictorial still camera negative film/process systems — Determination of ISO speed), which in the 'scope' section says: 'does not apply to motion picture, aerial photography, graphic arts, radiographic or micrographic applications, nor to negatives produced in diffusion transfer systems'.
And AFAIK there's also no ISO standard for black and white reversal.
So that's why is correct to speak about EI in cinematography, and not about ISO or ASA (which was the old american standard).
ASA speed is numerically speaking, basically the same as ISO speed: only the way of determining it changed a little.
Simply speaking, when a stock is rated EI 200, I set my lightmeter to ASA 200. It is because mine it's an old one: if it was newer it would have an ISO scale, and I'd set to ISO 200/24°.
And since ISO 2240 applies for non-professional colour reversal, here's why on old super8 K40 cartridge you could read ASA speed (and maybe, on more recent Kodachrome also ISO speed - who remembers it?). On modern Super8 E100 speed is rated in EI, probably because today is considered a 'professional' stock.
You can search (and read) ISO standards here: https://www.iso.org/obp/ui/