In the "How are expected missing transactions chosen to immediately forward?" section of https://bitcoincore.org/en/2016/06/07/compact-blocks-faq/ it states that "To reduce the number of things that need to be reviewed in the initial implementation, only the coinbase transaction will be pre-emptively sent."
I found https://github.com/bitcoin/bitcoin/blob/master/src/blockencodings.cpp#L23 which still lists pre-filling more than the coinbase as a TODO. I was wondering if that was in fact correct or whether it was an erroneous TODO. If not, is anyone working on that functionality or is there a reason it was never implemented?