Yeah, of course if you're just running through an in-memory slice and doing a little arithmetic on each item, sentinel errors and errors.Is might dominate your runtime. But the dominant use-cases (e.g. in the standard library) are syscalls, filesystem interactions, network APIs - you know, stuff that takes real time.
This reminds me of "latency numbers every programmer should know". Work with the standard library and other well-conceived go projects and you gain the intuition that error handling and bit-twiddling arithmetic don't belong together. That's the real story here, and OP's article is way wide of the mark.