Not to be that "ATOMIC LOVE=HG=HOS=DONALD TRUMP???" guy, but I see several similarities between AL/HG and John:
John ships from the same area as AL's re seller. They also ship first class (before anyone yells at me for discussing stealth or whatever, both HG and John have publically stated their shipping methods).
AL/HG also began offering blotters with mixed crystals as John does.
Before AL disappeared from TMG, he began to offer hash, which John also offers.
With all the weird debacles that panned out with AL/HG on TMG, it would make sense for them to begin to create a new identity.
Sorry for the 3 meo pcp conspiracy rambling. Also to clarify, this is pure speculation and something that has been on my high, dissociated mind.
EDIT: I would also like to point out that when John_ first appeared, he was both given an endorsement by JOR, and immediately stickied as a vendor on TMG (this has taken months for most vendors). This probably means he's a big boy who has been around for a bit.
They are all disciples of JoR afaik.