Regardless of the plausible deniability of the contents,
from a legal standpoint, if a court issues an order to divulge the contents and ownership of the box, the owner of the storage resources (banker) can comply, whereas the owner of the encrypted anonymous storage network node cannot.
I'm not going to make a blanket statement that this is a good or a bad thing, since it largely depends on what's in there (the technology itself is neutral); and some jurisdictions might define as depraved indifference (minimally) or facilitation (maximally) should the contents be illegal.
Also I can easily foresee that being unable to trace the provenence of data stored on one's node could put one in a difficult position to assert it isn't one's own, when possession is usually all that is needed for criminal liability.
The banker can cover the ownership case, and hence his backside.
As far as public/private goes, it seems this network from what I read, maintains an opacity shield with regards to contents, but is peer-to-peer storage. So in that regard, neither the safe deposit box nor the storage network are "publicizing" anything, per say.