I may be glitching a WoB. But are we really fully sure Wax and Wayne takes place after part 5?
All the WoB I've seen have said Mistborn Era 2 happens between SA 5 and 6. But in his original outline Era 2 is the Modern day Misting Swat Team stuff. Wax and Wayne kind of came out of nowhere. Also Harmony's talk about the outer threat could be something applying before SA starts just as easily as later.
I'm probably wrong on this, but it always stood out that Era 2 could mean a few things.