The mechanism presented of time travel in the fictional Avengers Endgame describes only being able to go back in time by starting a parallel reality and not actually entering the original time sequence. This would avoid the apparent paradoxes presented by interfering with the time traveler’s past and potentially un-creating the future they were coming from. Is this description at all accurate compared to how the extraterrestrials conduct time travel in reality?

In a word, the answer is "no." The concept of parallel lifetimes is of value in understanding the simultaneity of human experience—that all lifetimes occur simultaneously. These are, in a sense, separate timelines that occur in the Now. What the program in question describes is the inability to traverse time within the same reality, so going back in time would require opening a parallel timeline so there would be no interference with the prior reality. In actuality, in order for the extraterrestrials to do what they do, as you know happens, there must be ways to go forward and back in time within the current life timeline itself in order to be taken, advanced in time, and then be returned to the exact point or some other stage along the timeline to join up again with the self. That is more than going back in a parallel lifetime, maybe as an observer, but not influencing the current lifetime directly and thereby risking an adverse consequence. This is, in effect, an overriding of the prior timeline consequences, potentially, depending on how the time travel is orchestrated with respect to the points of departure and return. One can simply leave, go forward, and then come back to the same moment and thereby not influence the intervening sequence other than by coming in with perhaps new insights and armed with intelligence about what might be brewing having seen it first hand in the future, for example. But then one is simply creating a new future, potentially, and not uncreating a past. That is more difficult to imagine doing from a future vantage point because it presents the paradox of altering conditions and potentially threatening one’s own ability to be present in the future. As complex and fraught with peril as this seems, we can assure you that this can be done and is done routinely on a daily basis by many individuals among the extraterrestrials, as well as human recruits involved in the Mercenary Army Program, and done without adverse consequences. Things can change as a result, so this is in the eye of the beholder, whether something happens that is a benefit or a liability, that will, of course, depend on who is involved and the nature of the difference that results. The advantage goes to the individual engaging willfully in the time travel who has the ability to control things by virtue of deciding where and when to travel and how and when to return, so any manipulation they produce will play out and may affect others as well. This is normally something that would be done with great care and consultation among the affected parties to ensure there was a full understanding of potential consequences and an agreement by those involved to have the events take place. As you would expect, the Extraterrestrial Alliance simply does what it wants with no regard or consideration for the human consequences and this is typical of all of their behavior.