I don't think that's true. The 1 dose is still around 80% effective in preventing moderate illness and produces a good memory B and T cell response. The study you linked to that showed the drop to only 3% effectiveness is measuring effectiveness against preventing infection. Ultimately all the vaccines will have basically 0% effectiveness against preventing infection because vaccines don't prevent infection. So I don't think J&J had any nefarious motives. Actually weren't they one of the ones who were selling it at cost?
The reason I'm not going to stick with J&J is because they killed the vaccine with the big pause. So going forward we'll always be the bas step child that nobody outside of J&J will spend money studying.
The reason I will get a booster at all is because of future variants. Shane Crotty's work showed that with each exposure to the e (virus or vaccine) your immune system is predicting how the virus might mutate and building a library of antibodies against future mutations. Pretty amazing that our immune systems have learned that viruses mutate. I'm almost 100% sure I've had a Delta "boost" not too long ago so maybe in a month or so I'll go get a vaccine boost as well. I'm in no rush so I'll wait until there have been enough guinea pigs to trigger any safety signals if there are any, doesn't look like it atm. I think it'll be the moderna.