Apple has determined that a very small percentage of iPhone 8 devices contain logic boards with a manufacturing defect.
Affected units were sold between September 2017 and March 2018
As always these things are “a very small percentage.” The September to March window is a perfect fit with iPhone X NFC problem units and the Rev-B iPhone X production switchover.
Hopefully it will not be long before the other shoe drops and Apple issues a iPhone X Logic Board Replacement Program for the “very small percentage” of iPhone X units with defective NFC. The iPhone 8 Replacement Program came first because its logic board is much easier to replace, not so for iPhone X which is considerably more complex, and costly.
Until then, this will have to do for wrangling a Rev-B iPhone X from Apple.