Ian D's posts are pretty "ceterum censeo". Now matter how often you say it's a bootleg, it's still doesn't make it a fact.
Sweets on Soultown is produced by Nate Fortier/Tim Lawson. SG is credited to Nate Fortier/Tim Lawson/Tony Benton.
My guess is that in the early 70s Tony Benton and/or Sandy Golden got hold of the Sweets backing tape legally, recorded/overdubbed vocals, added new instruments/synths/accordions/ovomaltines/whatever.
Then they went to a pressing plant to get the record pressed. Incidently it's the same pressing plant that SS was using at that time for his bootlegs. Pressing plant offers label designs for their customers (as did many other plants) if they don't supply their own designs. Usually these pressing plant label designs were pretty generic, e.g. using the same limited range of fonts. That's why so many different record labels look similar.
Eventually record got pressed, probably very limited run maybe 250/500 pieces. For whatever reason record was never properly distributed. Maybe they intended to sell it at gigs but failed? I don't know and I don't really need to know. It's a pretty rare record and not the first rarity to turn up in unplayed condition, even after 40+ years.
Re. the theory that SS himself recorded/pressed the record. That's bullshit. Record way to slow for the UK scene at that time. And if he had done it to show the world what a good producer he is, he would have put his name on it.