Of course you can, but that's not what's implied by the quote.

In addition to microtonality, many instruments (and the human voice) are capable of infinite tuning, and musicians will deviate from the "correct" note (as played by an even-tempered instrument) based on chord structure, voice leading, etc.

That's clearly not what was meant, even without the context of this following bit:

> To describe tones that exist in music, we can describe tones that exist on a piano. There are only two rules:

> the first key must play a tone of 27.5 Hz each next key must play a tone 6% higher than the previous key

(This is not to mention that at a 1.06x increase per half step you're going to be sharp by 1 cent / octave which starts to add up).

there are absolutely pitches that an arbitrary piano cannot be tuned to. it is also non-trivial to tune a piano.