There is also a logical problem with that hypothetical quote. And that is it would only serve as a deterrent for those who want enlightenment, it would be demotivating. In later Mahayana teachings there are talks about the Dharma ending age where enlightenment is near impossible, however, there is always a special teaching that one should use instead of the others and that guarantees success.
"If the Buddha-Nature is seen, there will be no seeing of a nature in any thing."
(Nirvana Sutra, T12n374p521b3; tr Yamamoto)
"Neither cultivation nor seated meditation — this is the pure Chan of Tathagata."
(Mazu Daoyi, X1321p3b23; tr. Jinhua Jia)
“Don’t rashly seek the true Buddha;
True Buddha can’t be found.
Does marvelous nature and spirit
Need tempering or refinement?
Mind is this mind carefree;
This face, the face at birth."
(Nanyue Mingzan: Enjoying the Way, tr. Jeff Shore; T2076p461b24-26)