You can already do some of that without the dynamic linking feature. There is a JS API to instantiate a WebAssembly module, providing JS functions that are callable as external functions from within the WASM module. Conversely the WASM module exports functions that are callable directly from JS.
This allows rudimentary interop between JS and WASM, and dynamic linking will make it possible to deliver your WASM application in separate pieces, e.g. a large, rarely-changing library that is cached, precompiled, by the browser, and a small, often-changing application piece.
This allows rudimentary interop between JS and WASM, and dynamic linking will make it possible to deliver your WASM application in separate pieces, e.g. a large, rarely-changing library that is cached, precompiled, by the browser, and a small, often-changing application piece.