SSNs are entirely insecure as mentioned earlier in this thread. Geographic prefixes are a drop in the bucket on that front.
The post that I replied to is almost entirely incorrect as it relates to available SSN “keyspace” (misnomer), uniqueness, etc.—-for which geographic prefixes and group numbers are relevant.
I supplied direct sources, so no idea what your “even if what you say were true” skepticism is rooted in.
Even if what you say were true, handwaving this as unimportant because it only affects people over the age of ten seems a bit silly.