If it can see the probabilities of alternate futures years down the line, and act on them in order to plant seeds that will bloom exactly when it needs them to, then it's not unlikely or impossible that the Thunderhead made itself a massive part of Greyson's life as a child intentionally so it could manipulate their bond to use him as a pawn at the point it needed his service during the second and third books. In other words, it's not out of the realm of possibility that Greyson was, in a sense, raised as a child sleeper agent, and never knew. Worth noting that a child in his circumstances, who was functionally an orphan, would imprint heavily on the first figure of authority to show him affection, and the Thunderhead probably knew this.
If the above is true, how many other Nimbus agents throughout history has the Thunderhead "groomed" for service in this manner?
Since many Scythes end up losing contact with their families, and end their term through suicide, there has unquestionably been more than a few cases where a family who thought they had immunity became subject to a gleaning they weren't expecting because their Scythe family member, who was keeping them immune, self-gleaned without their knowledge. (Unless the Scythedom takes it upon themselves to notify next of kin when the seventh commandment is invoked)
When Goddard tries to wipe out the Tone Cultists, Mendoza tries to get the Cultists to fight back and kill the Scythes. This is bad enough until you remember that Scythes kill the families of people who resist their own gleaning, meaning if Greyson hadn't stopped him, Mendoza would have caused the deaths of potentially thousands.
