Hello, according to upstream, the default behaviour for rawtherapee-4.2 and later should be to set DCACHE_NAME_SUFFIX="". This is to limit end-user headache in manually porting config files every update.
Link to discussion: https://code.google.com/p/rawtherapee/issues/detail?id=2427#makechanges
Only 4.2 isn't in the tree (yet).
Fixed in 4.2 in the tree.