Yes you are correct on the fuel tank issue, and this isn’t the first time they’ve got it wrong. Heljan’s previous release of 33111 had the later type of fuel tank fitted, when 33111 actually carried the early type fuel tank with the cutaway throughout its entire life and still does to this day.
33111 is the only 33/1 to still have the early type fuel tank fitted.
Heljan should really supply replacement fuel tanks free of charge to enable purchasers to correct the appearance of their locomotives.