The config.boot file exactly replicates the config that I posted earlier, and has the desired ordering.
However, no rename is happening during boot (unlike what happens in the 1.4 rolling release running on the working machine
Version: VyOS 1.4-rolling-202104260417
So, it looks like somewhere, we lost the code that does the interface renaming during bringup (using the renameN placeholder name).
Basically, ifconfig or ip int shows the links as discovered, vyos reports the new mac addresses.
The end result is no-one talks.
Christopher