That stuff is basically just a mix of solvents and probably won't work on a fuel tank. I looked up the SDS, I think the MEK is the only ingredient that would react with HDPE.
https://www.rustoleum.com/MSDS/ENGLISH/281215.pdf
Might work but you'd still need a filler/patch material to fill a crack. I think I'd still go with the tech-bond system if I were to try anything.