Facebook didn't do any extra engineering work, they just specced less sensitive Rx parts with the optics OEMS , and 1dB less powerful Tx.
I guess that depends on how you define "engineering."
They're basically trying to create a new class of transceiver. It remains to be seen if this will take off or not, but since it is part of the OCP effort, the chances are good that it will be taken seriously by QSFP vendors.
OCP is generating a lot of activity and change on the networking side. Whether it just becomes a race to the bottom where only the giant suppliers survive or whether it creates a new eco-system with more players and interesting technology remains to be seen.
I think in order to bring more OEM vendors in we need to see the other big players to also accept the relaxed specs.
Hopefully, we don't end up with another dozen different 100G or 200G MSAs that work from 15-55C.
I would guess the NRE to develop either is similar and that the design for either is almost the same. Perhaps Facebook is just trying to get the optics cost down by negotiating discounts on the non-yielding MSA parts that would have otherwise had to get thrown out?