It is marketing whatever way you look at it.
The title has been changed on home video packaging for years to unify the series. This is nothing new...
The Final Conflict is called Omen III The Final Conflict on latter VHS, DVD and Blu-ray. The onscreen title remains The Final Conflict, just as the onscreen title for this is Raiders of the Lost Ark.
For something like Star Wars it's different. The onscreen title since 1980ish has been Star Wars Episode IV A New Hope. This was the title it had when most of us saw it probably. We tend to refer to it as Star Wars, just like we tend to call next one Empire and the next one Jedi. As in, 'I've seen Star Wars, Empire and Jedi, but not Revenge of the Sith' for example.
Most, if not all, movie guides refer to this as Raiders of the Lost Ark, no matter what Lucasfilm might wish to call it.
I have seen Star Wars in the cinema in 1977 there a lot of members on HDN who seen Star Wars film in 1977 when first released or saw when released again in cinemas in 1978/1979/1980 if you not aware so it's not most of us who saw the film with the new title IV A New Hope
The difference with Star Wars was there was sequals that happened later that led to change to the title Episode IV A New Hope
in 1981 a year after Empire Strikes Back was released
Cinema re release in 1981 used the new title Episode IV A New Hope and also in 1982 and later years
Later a re-edit of the film in 1997 led to have title on screen also changing to Episode IV A New Hope but was known as Episode IV A New Hope since 1981
When Star Wars was created in 1977 they did not have have plans for sequels to be made
20th century fox did not even know in 1977 if the film was going to be a massive blockbuster hit or a flop until after the film was released and no reason at that time to have the title Episode IV A New Hope
George Lucas himself officially retitled Raiders of the Lost Ark to Indiana Jones and the Raiders of the Lost Ark
in 1999 it was not a Paramount decision
Yes the title is still Raiders of the Lost Ark when watching the film on screen but the title was still officially retitled even if you don't see that name change on screen when watching the film
In regards to The Omen films and Star Wars films they have nothing to do with Indiana Jones films apart from they also had sequals made but so has a lot of other films over the years
The next Indiana Jones film in 2023 wiill have in it's title Indiana Jones and the ?????? (?????? = The rest of the title not officially reaveled yet)
Reason why the next film in 2023 will have in it's title Indiana Jones and the is so it matches the other previous films that have Indiana Jones and the
Indiana Jones and the Raiders of the Lost Ark
Indiana Jones and the Temple of Doom
Indiana Jones and the Last Crusade
Indiana Jones and the Kingdom of the Crystal Skull