Shelley 12 Word Wallet
I was working with the cardano example code and noticed I could create a 12 word shelley era wallet and get outputs. From the cardano docs I've seen, I thought at least 15 words was required to create a shelley era wallet with "addr" addresses. Is 12 words in the shelley code valid? 

This is however counter to trustwallet and exodus that provide 'addr' addresses but only have 12 word recovery phrases. 

Are trust & exodus 'byron' era but are doing a 'addr' address derivation? Documentation from Cardano is poor and not kept up to date. 