I have a degree in economics. One of the earliest concepts taught in intro microeconomics is comparative advantage. It describes how when people who specialize in what they're good at, and don't do the thing they're bad at, and then trade with other people makes everyone better off. You should always take the route where opportunity cost is lowest.
To put this in Target-speak, imagine you have two team members. One is a rockstar GSA, the other is an average perfoming hardlines TM. In this world the GSA is better at both roles. If placed in either role, the GSA performs better than the hardlines TM. BUT, the GSA is better at doing GSA stuff than hardlines stuff. It makes much more sense to put the GSA in a GSA role than the hardlines role. Let the excellent performers do what they're best at, and let the average performers do what they're best at GIVEN where everybody else is best at.
This idea that everyone can do everything flies in the face of what economists have known for the past 300 years.