Stern was trialing these new insert boards over 2 years ago when Gary Stern went to China and had a full game converted over to modular boards under the playfield with Leds. There is a video around with a few machines down the back of the factory with 2 x machines fully converted over. I know they have been working on the new backbox boards off n on for the past 2 years as well.
Now that demand is up, and Stern has the funds, it looks like they are pushing ahead with the different design from over 2 years ago.
Imagine the machines in 12 months time, will have some cool features. Last of the last will be Avengers probably before the new boardsets n new modular cabling n under playfield boards.