This change affects the quality of platform abstraction.

The code inside tsc does not care about the return from setTimeout (indeed, it's declared as any). Also tsc doesn't require the rich extra parameters and fancy spread args.

Effectively you're making the abstraction layer very needy and very tied to one specific platform (node) — whilst the code using that abstraction doesn't even care. It defeats the purpose of having abstraction in the first place. Rather than provide a small easy-to-control gateway to the platform this slowly grows to encompass every feature, and in ad-hoc inconsistent way too (consider Object.create which isn't as omnipresent yet is used indiscriminately unabstracted).

And of course ChakraHost fails to allow for setTimeout too! Naturally, as this addition is an ad-hoc artificial extra way out of sync with the intention of sys interface.