Might be intended to preemptively deflect criticism of "reinventing the wheel"/solving subproblems in a non-standard/convoluted way.

I'd expect an engineering project with "no prior experience" to take weird/experimental approaches more often compared to a "from scratch" project (where I would expect proven minimalism instead).

This person made it from scratch with no prior experience, so the bragging rights are well earned.

"from scratch" and "no prior experience" have very little in common.