First of all. Strictly speaking, there is no such a thing as a TS runtime. TS compiles to JS.
Second of all, bun binds against JavaScriptCore, which is the JS engine used in Safari. Node binds against V8, which is the engine used by Blink (Chromium et al). Both are implemented in C++. And the latter is considered the fastest engine.
Ironically, both engines are mentioned by name in the very bun blog post being discussed, which points to a problem that is almost bigger than mere tech literacy from the pseudo-intellectual OP.