Steamings damage corks, especially sterilizing ones. Their number should be minimized. Now for bottling, I do not think it is important for corks to be sterile, as anything worth of corking will kill whatever might be living on cork surface. Sanitized is enough.

Now repackaging is another beast. Once packaged, corks are left for indefinite time, and if inoculated with something that might survive on bare cork (pretty much this means fungi), it might become a nice growth media. Then, steaming might kill it (and if it is not pressurized, that would not kill spores), but it will not clean it from the cork.

So, on small scale, it is not very important, some corks might get spoiled occasionally. But 6000 is no small scale lol.