I'm not sure I understand what you're saying. There are two core principles behind WebAssembly. First of all you can run low level programming languages like C on any architecture. This is possible if the code is available and you are willing to compile the C code before installing the application (see gentoo). Secondly the libraries/APIs that the program depends on must be available.
What you're saying is that every vendor shipped their software with source code and only used cross platform APIs. Is that right?
What you're saying is that every vendor shipped their software with source code and only used cross platform APIs. Is that right?