Do you get the benefits of a B-Tree in a managed language?

Question

My understanding is that one of the key features of a B-Tree (and a B+Tree) is that it is designed such that the size of its nodes are some multiple of the block size of whatever media the data is stored on.

Considering that, in a memory managed language like java/c#, we don't really have access to how, when and what order, data is accessed from the drive... can we still predictably benefit from the major advantage of this data structure?