I ran into this too – created a ranger alt right after the patch went through and checked today after finding out about this. My account now has all of the GW1 achievements, which it shouldn’t.
I do have a GW1 account but it isn’t linked to this account and I never really got far enough into GW1 to get many or any of the achievements.
EDIT: I filed a bug report about it as best I could considering the condition of the bug report tool. Hopefully this gets straightened out fairly quickly.