Oh yeah, to summarize what I now know I don't know I'm now unsure if 2002 EFI bikes:
Really were all Delphi
Really were originally Marelli with a running change to Delphi
or, perhaps....
Really were all Delphi but had a running change that went from a pressure line and a return line to a later use of the now common single pressurized fuel line. If this were the case, however, one would expect to find different part numbers in 02 for the different tanks or throttle bodies/fuel regulators that accepted the lines. Such probably wouldn't be Marelli holdovers (though this is based on nothing more than that 02 specific line cover seeming to wrap around lines of two different sizes while the Marelli lines were the same size).
Since there seem to be no other 02 specific parts for a Delphi variation this seems to suggest a Marelli carryover simply using old part numbers. Even though that doesn't explain the odd 02 specific fuel line cover. All of which says I still really don't know what all I might not know here

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Also, I'm glad my tank has the (hopefully) standard and expected single line fitting. With any luck it means I won't have to screw with any of this weirdness.