Performance against JavaScript for specific use cases (i.e. being a general purpose VM for traditional application code) is a factor. Performance against JavaScript in general (e.g. calling the same simple function in a loop) is not a factor.
E.g. if you had only done rendering on a CPU and someone came by and said "we can do all sorts of stuff we couldn't do before with this GPU check it out!" it'd be easy to say "I could do all that on a CPU" and you could even show the exact same benchmarks presented here and then say "see, the CPU even runs the single threaded factorial function many more times per second than this new GPU". Everything you said would be absolutely correct in the most literal form yet it'd still be completely missing the point of why the GPU was made and how to assess if it fits that purpose better.
Then someone shows you the GPU doing rendering it was designed to do well better than the CPU and the reply is "So it is about the GPU being faster than the CPU?". Yes. No. It depends what context you're asking from. Traditional use cases no, what it was designed to do well yes.
The original article which talked about WASM being slower itself specifically notes this relation of purpose, functionality, and performance it's just tucked away in the conclusion:
> definitely don’t go converting all your websites’ JavaScript to WebAssembly! However, that’s not really the aim of WebAssembly. Its aim is to enable richer experiences on the web that require higher performance, for example machine learning, virtual reality, or gaming.
E.g. if you had only done rendering on a CPU and someone came by and said "we can do all sorts of stuff we couldn't do before with this GPU check it out!" it'd be easy to say "I could do all that on a CPU" and you could even show the exact same benchmarks presented here and then say "see, the CPU even runs the single threaded factorial function many more times per second than this new GPU". Everything you said would be absolutely correct in the most literal form yet it'd still be completely missing the point of why the GPU was made and how to assess if it fits that purpose better.
Then someone shows you the GPU doing rendering it was designed to do well better than the CPU and the reply is "So it is about the GPU being faster than the CPU?". Yes. No. It depends what context you're asking from. Traditional use cases no, what it was designed to do well yes.
The original article which talked about WASM being slower itself specifically notes this relation of purpose, functionality, and performance it's just tucked away in the conclusion:
> definitely don’t go converting all your websites’ JavaScript to WebAssembly! However, that’s not really the aim of WebAssembly. Its aim is to enable richer experiences on the web that require higher performance, for example machine learning, virtual reality, or gaming.