Even though Tyson can clearly remember his childhood with great clarity, it is very difficult to trigger nostalgia for his childhood.
A lot of that time, though clearly remembered, is suppressed on an emotional level for Tyson; similar to some of the time he spent on the run with The Colonel. It’s as though he spent those years watching his own life through a window; aware, yet notably separated.
Pangs of nostalgia for his years in the army are incredibly easy to summon - antiseptic and memories of John’s laughter, overripe fruit with Captain Samson’s voice, old PS3 era games with free time between rounds in the compound - but anything before that time is near inaccessible.