The 'Italia' on Map appearance chart has some differences to the original OB's - is the Italia chart thus the definitive
The Basic Game OB on the map is in accord with the 6th edition rules. The Advanced Game OB on the map is in accord with the 4th edition rules. The Advanced Game rules are under development and updating is anticipated with the 7th edition rules. There will probably be further changes to the OB at that time.
There were differences between the 1st and subsequent edition rules regarding OB even though the unit counter identification and values stayed the same.
Nothing with this game is as yet "definitive." If you intend to play someone else, insure that you are both using the same version of the rules.
Likewise, the Game Turn Record chart available at BBG - much less Rps for both side.
The 2nd edition white "Advanced Game Turn Record Card" scan on BGG replaced the pink "Game II - Time Record Card" of the 1st edition Anzio.
Finally,is only the 'Step Reduction' table now used and not the Unit Elimination Table?
The "Unit Elimination Table" was only used with Game I of the 1st edition Anzio. The "Step Reduction Table" was used for Basic and Advanced games in subsequent editions.