They're not really the same: you know that an async function may potentially suspend and have other code run before its completion, while a normal function (in the absence of threads and signals) is guaranteed to run atomically, at least as far as your process's memory space is concerned. You also know that the only points at which an async function may suspend are an 'await' statement, and so data invariants that don't cross await statements or other async function calls can be reasoned about as if you had purely sequential code.

That's precisely the coloring that makes async useful. Without it you need to explicitly protect all shared data with mutexes or other synchronization primitives. 40+ years of threaded programming has shown that programmers cannot generally be trusted to get this right, and this in an area ripe with bugs.