Because he also possessed this strength!
Ever since learning Turning Stone to Gold, Yi Chen has been reversing not gold most of the times daily, but his own Cultivation Body. Speaking of understanding his own Cultivation Body, of course, no one understands it better than he himself does.
Although his master Yi Chengzi's reversal of material purity is not yet high, relying on the negligible strength emitted by the Black Hidden Buddha, he even felt that his Cultivation Body's bizarre devouring ability, after paying a huge price, might be able to nibble it away entirely, not to mention he also possessed Divine Skills by his side.
"This...this is impossible!"
"This is the power of Dao Fruit, this is the strength of Dao Fruit! I cannot sense this essence erroneously! Although this strength is not complete, it has indeed gained insight into a bit of the essence of Dao Fruit."
