If you do not understand that "embarrassingly parallel" is a technical term and that it's generally understood that most programs are not easily parallelizable, there is not a discussion we can have here.
Burntsushi began with "here, parallelization is beating out memory locality and optimization in its impact," but explicitly declined to generalize this the way you generalized your claim about memory.
He further pointed out that ripgrep is fast not just because of parallelization, but also because of how it handles memory.
Then you come back with "you can't always parallelize this well" (which burntsushi agreed with from the beginning) and "you also need to deal with memory" (which ripgrep does)? How is this burntsushi's problem with understanding "embarrassingly parallel" and not your problem with understanding Rust?