I can't, I ported Adventure Game Studio runtime for Webassembly, currently I have two versions, one using single thread, and one multithread using workers. I plan to use the single thread version since it doesn't require these headers.
The port was done using Emscripten. The SharedBufferArray restriction is documented in the previously provided links and it's the memory area used for communication between threads (workers).
This is due to pthreads implementation on Emscripten, detailed here:
https://emscripten.org/docs/porting/pthreads.html
The headers are unfortunately a requirement when using Emscripten pthread implementation.