Actually, I think it is because you separated the clutch fluid. I have been trying to make this point everywhere. The C5 and C6 Corvettes that come with that little clutch reservoir are notorious for sticky clutch since the little clutch reservoir is just not big enough to provide enough fresh fluid to cycle through. It seems GM understands this issue, and Gen5 Camaro (which was released 5 years later) comes with a huge brake fluid reservoir serving both the brakes and the clutch. I used to change the clutch reservoir fluid all the time when I owned Corvettes, but I don't even bother with the Camaros, and everything is running fine.
If you have contaminated the slave cylinder to the point that it does not seal as good as it normally does, this will get worse in time even if you keep the fluid clean or even get it flushed. I would hope not. I highly recommend you ditch that little cute clutch reservoir
In an ideal world, you would have big reservoirs for both the brakes and the clutch separately.