Danellians

In case anyone new is reading, in Poul Anderson's Time Patrol series, the Danellians are the evolutionary successors of mankind who found the Time Patrol to protect the evolution and history that led to them. They do not ban time travel because it is part of the process that led to them. (Neat.) Right at the end of the series, we learn that, even if there were no time travelers, random fluctuations in space-time-energy would alter the course of events so that the Patrol, continually counteracting chaos, is a necessary stabilizing element. I think that the Danellians would become aware of any alterations only if they traveled into their past and returned to an altered present but maybe they do want both to time travel and to ensure that they return to their preferred version of the present?

Why is it that the Danellian who appears in the opening story is a blazing shape whereas the one who appears near the end of the series is a stranger on the shore?

"'...no doubt they can disguise themselves when they want to, go among us in the form of human beings...'"
-The Shield Of Time, PART TWO, 1987 A. D., p. 29.

Everard explains to Wanda that, without a Patrol:

time travelers would deliberately or accidentally change the past;
thus, everything futureward would be different;
this would happen repeatedly;
the result might be complete chaos or human extinction;
in any case, time travel would be prevented.

So maybe that is the universe that we are living in? This is Larry Niven's argument, summarized in the combox here.