well
a) JT isn't their season. That team isn't good enough to win with or without him
b) if he sits out half the season, the rest of the teams in the league will see that. And they'll know what he'll do any time he gets disgruntled about $. Just like if he comes back and decides he wants to "fake an injury", everybody else in the league will see that too. Not like the Colts won't put that out publicly either, much in the same way John made it known that Dobbins was "healthy" but no participating in camp. Everybody knows what's what at that point.
c) by sitting half the season, JT also forfeits half the franchise tag $. Which is a gigantic amount of $ to him. And at that point, the FA market will have been set for high-end RBs (which will be lower than he wants anyway), because there's about 8 really good RBs who are all scheduled to be FA's in 2024.
So he'll wake up mid-way through 2025, realize the $12-13M on the FT was actually really, really, really good value for his services, given what other players will and won't get in FA, and then realize "fuck I should have just played".
Hence why this isn't close to a 50/50 risk.