The badBIOS story is frustratingly short on details but this confused post seems to be making a lot of assumptions which add restrictions and then argue that it's impossible because of those guessed details:

1. He wastes time talking about “high frequency” as if it means radio EFI, which was never claimed and is an odd tangent.

2. Apparently at some point he actually read the original claims and realized that they were talking about sound and then makes the claim that this is simply impossible due to hardware limitations. See e.g. the running code at https://github.com/borismus/sonicnet.js demonstrating why this claim needed more than his personal assertion to be considered truth.

3. The main logical fault is the extended discussion about how limited the BIOS environment is, apparently under the belief that somehow everything must be implemented at that level rather than, say, shipping with different versions for various manufacturers which use that as a way to inject the actual payload into the OS. Put another way, what are the odds that someone would be competent enough to build any of the other pieces but not realize that you can do hardware detection and build a library of exploits for, say, common Mac laptops?

4. Claims about being able to catch this trivially by dumping the BIOS are suspect unless he's talking about extracting the chip and reading it on a known-good system — anything running on the suspect box runs into a textbook trust problem which isn't even acknowledged in this post.