[chadhietala1]

Yea this is sort of a relic of the initial VM architecture we landed originally in Ember 2.10. That architecture was more like Clojure e.g. read -> compile -> execute. So the nested arrays are seen as sub expressions. You are correct this can be linearized.

[wycats]

Also, this particular format is the "wire format", which is the compact representation that we compile templates into to send to the client.

The client then compiles that representation into flat opcodes, in part by specializing the template based on runtime information (like the exact identity of the components in question).

The runtime opcodes are binary (128-bits apiece at the moment) and optimized for reasonably fast iteration. The wire format is, as chadhietala1 said, not as flat or compact as it could be, but still much more compact than our earlier representations (or the representations of competing rendering engines).

We plan to improve the wire format representation in the near future.