Don't know if is a bug or I miss something, I use default configuration for in memory repo, this is the behavior:

Create a tree of 3 node: '/a/b/c'
Create a node 'tmp' under the root
Query with SQL2 to get all ISCHILDNODE under path '/a/b' return node 'c'
Move node 'b' under '/tmp'
Call getNodes() on node '/tmp/b' return node 'c'
Query with SQL2 to get all ISCHILDNODE under path '/tmp/b' return no node
Query with SQL2 to get all ISCHILDNODE under path '/a/b' still return node 'c'

Same behavior with ISDESCENDANTNODE.

To return children with ISCHILDNODE or ISDESCENDANTNODE query, you have to update the children