Well, you are assuming things are doing to get better. They might. But right now it's a 6-10 team off to its worst start since the year they had the worst record in baseball. I'm not saying I think this team isn't going to find itself and start playing better than .400 ball. But if they are a .400 team on July 20 they won't be adding talent. And if they are a .450 team they'd probably be dumb to do so. Like the ostensible reason for finally exceeding the CBT, you make big moves (and give up prospects they still desperately need) to go from a good team a a potentially great one, not to go from the same old mediocre team to last wild card.
It wouldn't just be Segura - Eflin, Knebel, Gibson, other relievers, and maybe you get the early jump on Hoskins. If they are a bad team.
Regarding Segura's option, probably 80-90% of the time both sides are happy to move on in those situations, and while the player doesn't take it personally, they also don't take less money from their old team if they can get more from another one.
Segura's been a perfectly decent player but moving on from someone who has never been on a playoff team and has been a constant on this incredibly blah era isn't gonna break my heart.