Actually, this used to be true many many years ago...
This was done at the request of Delta Air Lines, because SkyMiles Gold Elite at the time had roughly the same threshold as Flying Blue Gold, but Delta didn't grant the ST Elite+ tier.
In order to avoid any arbitrage between DL SM and AF-KL FB programs for U.S. and Mexico based members, it was decided that FB Gold Elite members in the U.S. and Mexico would only be ST Elite.
Strangely enough, Canada was excluded, so I basically used the address of a friend in Montréal to be my residential address to make sure I would be ST Elite+. A little bit complicated because my froeld would have to forward to me all the FB mail (member card, luggage tags etc...) and I would need to remember the address every time I was calling FB North America, because back then, they asked for your address to check your identity.
Interesting fact is that on the older FB cards, you would have "SkyTeam Elite" pre-printed/pre-made for Silver cards and "SkyTeam Elite Plus" pre-printed/pre-made for Platinum cards, both under the SkyTeam logo in the top right corner, but for the Gold card, you could see clearly that the mention was engraved at the same time as the name and number are printed for the member, allowing to either print STE or STE+ depending on the residence.
A couple of years later, Delta modified their program so that SkyMiles Gold are now recognized as SkyTeam Elite Plus. Since then, there was no longer a reason to differentiate U.S./Mexico FB residents, and that caveat finally was lifted.
I happily switched to my real U.S. address at that point (I became Platinum and kept the status consistently so it wouldn't be an issue any longer anyway).
The blog's info is outdated but they were technically right... a couple of years ago!
Cheers,
Vinnyc