The inclusion of "otherwise" was clearly inserted as a modifier to distinguish its difference to "subordinate".
By your own admission, "diminish" means to reduce. How much more clear can it be.
They are stating, the DB claim will neither be made inferior to "OR" otherwise (else; apart from that) reduced as a claim.
The "PROOF" is that the FDIC stated such, and no further "PROOF" is necessary. It's a signed agreement!!!
In term of the claim that I somehow selectively included only "tidbits", to skewer it's meaning is false.
I clearly posted the whole paragraph, which clearly shows the context was unchanged.