I think the idea behind keeping 2.11/2.12 as similar as possible is to enable people to cross-build things more easily, which would drastically improve the life span of the last Java6-compatible release (2.11) until people have found better solutions.

(I can imagine that there will be generic translators from Java8 bytecode to Java6 bytecode, so why should they keep maintaining two backends, if they could maintain one and just leverage a common tool to do the rest?)