Reshetnikov didn't confess to them being reverse engineered, though. He confessed to them being conjecture arrived at after working on the problem for a bit by tweaking similar integrals in symbolic math software / numerical approximations. Every post was a gamble because it could have been wrong.
Of course, that could be a lie, but he came clean about other things that make sense retrospectively.
Of course, that could be a lie, but he came clean about other things that make sense retrospectively.