He is not using it incorrectly:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Idempotence#Computer_science_meaning" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Idempotence#Computer_science_m...</a><p>React views are idempotent.  They are not necessarily pure (though they can be).