platformName where the browser is remote to the endpoint node

[gsnedders]

The current definition of platformName is:

Identifies the operating system of the endpoint node.

…where the endpoint node is the final WebDriver protocol hop.

This seems somewhat surprising with, e.g., SafariDriver connected to an iOS device. The OS of the endpoint node is macOS (because that's where the final WebDriver HTTP server in the chain is), but that doesn't seem anywhere near as interesting to the end user as the OS on which the user agent is actually running. And indeed, SafariDriver seems to deviate from the spec here, returning iOS.