They ask the manager, "If you want twenty tickets, just ask me for twenty tickets. Why do you set fifteen as the standard, and then try to use cheap psychological tricks to get me to do twenty tickets?"
I have managed teams going back to the nineties. If I want fifteen tickets, I ask for fifteen tickets. If someone just does the minimum, they just get paid the minimum, but I have set my expectations such that their work is a net benefit to the company, so they keep their job.
If things change and I need twenty tickets, I will ask for twenty tickets. It's not complicated. The "bare minimum" is still enough to keep a job. If it isn't, it's on me to establish a different minimum such that the "minimum" is exactly that: The minimum needed to remain employed.
"Dead weight" is someone whose work is not a net benefit to the company. If I as a manager set a minimum, and someone does the minimum, and they are not a net benefit, WTF am I doing as a a manager setting fifteen tickets as the minimum?
Employees meeting expectations but not being a net benefit? That's a management problem. And if it's across the org, that's a SYSTEMIC management problem.
So if this person is meeting the minimum, either they are NOT dead weight, or there is a management problem. Either way, they are not the problem.