Barty Jr. saying now that the magic he wanted to create required material elements did not make Manus think he was making such a choice to lower the casting threshold.
Having spent so much time with Barty Jr., Manus understood his personality even better; although a lack of security caused by certain family reasons did indeed exist... his ambition was still very high.
This could also be seen to some extent from how he had once used a thesis to test Manus.
Now that Barty Jr. wanted to create his own magic and had intentionally chosen magic that required casting materials, it could only be because he had higher pursuits.
Magic that required a werewolf as material?
Amidst a subtle expectation of wanting to see what kind of flowers the seed would bloom into, Manus did not ask too much, only reminding Barty Jr. not to do anything immoral.
Being morally perfect was difficult, and even he could not manage it, but easily trampling on morality was also something he could not tolerate, even if this world lacked fairy-tale traits.
"Don't worry, I know where the bottom line is."
Just as Manus had come to understand Barty Jr. through their time together, Barty Jr. was simultaneously understanding Manus, and was very clear about his style of conduct and treating others.
It was also largely because Manus himself was actively using his own way of handling matters to influence them, especially the choices he had made and what he had said to them during the Quidditch World Cup previously.
Manus nodded.
Perhaps the two of them did not have identical understandings of the finer details of morality, but morality was inherently like this; having a clear conscience was enough.
Barty Jr. also left.
Manus stayed a while longer at the top