So, the list of "previously secret sins" is not a ranking of "badness". Desecrating a Eucharist isn't "worse" than genocide. It's not "better", either. Desecrating a consecrated Host is a foundational sin- it strikes at the heart of what it means to be a Catholic. So it requires more steps not because it's so bad, only a pontifical commission can absolve it, but because you've basically acted against the basic nature of Catholicism.  