https://commons.wikimedia.org/wiki/Special:CentralAuth/Alexis_Jazz shows I registered in 2008, but I have a welcome message from 2007. @Fae said on https://commons.wikimedia.org/w/index.php?title=Commons:Village_pump&diff=300160331&oldid=300159265 "That's a GAM bug as commonswiki_p has your registration date at 2007-10-13 05:23:20."
The date in the header from 2008 is the creation of the global account (it is in the section ("Global account information").
The date in the table has a header "Attached on", it is not a creation date of your commons.wikimedia account.
For newer account the timestamp on the local wiki and in this list are the same, because new accounts automatically are attached to the global account, but for older accounts it is possible to have different dates here.