If it wasn't for Flandre's candidness, Lin Xun would have had no clue of Firefly's hidden trump card.
If things were to proceed as Firefly had predicted, after the Wet Nurse was eliminated, he would be completely controlled by Flandre using the 'Hive Mind'.
No! Flandre would likely take full control over him the moment it seized the Demigod Shell and confronted the Wet Nurse.
Only in this way could the successful execution of Firefly's plan be ensured.
Flandre would control him, drawing on countless Malignant Thoughts as a source of power to annihilate the Wet Nurse's new body and consciousness.
Then all beings that had been corroded by Malice would be transferred to an independent consciousness network, with all existing beings on it wiped out, including both him and Flandre.
Upon agreeing to Firefly's plan, Flandre knew that its own ending would be death.