I think you're right.
DWG 38 has mentions F-821BPP on both sides of the baggage door. Those parts have different rivet spacing. I gather the original fuselage was not pre punched, so the support strip would have been identical prior to drilling. But these are PP or pre punched! Possibly an error when pre punched parts were introduced.
DWG 84 calls them F-821C-1, meaning it's for the -1 fuselage. There was a design and parts revision, and the error was corrected.