For the Lord of the Flameless, whether he could obtain this human actually was not important.
Even if this human initiated the Transmutation, it was merely the Cruel Scholar invoking his will.
Even when facing the Cruel Scholar directly, the Lord of the Flameless would not be at a disadvantage; he could even use this opportunity to negotiate some conditions, to gain some benefits.
As for Popota's belief that "only another Demon God can defeat a Demon God," this view was actually incorrect.
It was also a reflection of Popota's lack of understanding of high-end combat power.
Demon Gods rarely fight among themselves; even the likes of the Unparalleled Great Demon God, who had previously reigned, would avoid needless waves, let alone He and the Cruel Scholar, both being Great Demon Gods.
Therefore, the Lord of the Flameless did not care whether this human would initiate the Transmutation or not.