Elias taking on a similar, if not a completely identical, appearance to Lindel when dealing with non-sorcerer/non-mage humans, or whenever he’s out among the general populace may seem a little odd, as there is no indication that his shape shifting abilities have limits preventing him from creating a unique disguise of his own. He probably feels that going through the effort of creating his own disguise is wasted when there are millions of children around the world who could quite easily see through the illusion and most would find his true appearance frightening, thus potentially drawing unwanted attention to himself. However, he does need to interact with the outside world on occasion, so a good disguise is necessary. Why Lindel’s? Most likely, Lindel’s the one who taught him how to adopt a human appearance, and stressed the importance of taking on a form people would find approachable, even friendly. Elias, being Elias, took this to it’s logical extreme by adopting Lindel’s appearance. After all, Lindel was the first human friend Elias ever made, and the one he’s known and interacted with the longest.
Except he looks more like Simon than Lindel, and the author has mentioned Elias is supposed to have based his form on the priest and not his old mentor. The sentiment of doing the bare minimum to pass for human while avoiding meddlesome troubles like being mistaken for Simon in public does hold water though, as we do see later on in the series he is more than capable of making more "unique" human forms. Though when Elias did enter a monstrous state where he did have human-looking hair, the anime made its color closer to Lindel's than the darker blond of Simon and Elias' human glamour for whatever reason.
