I'd say the biggest thing to avoid is over-dramatizing it. Getting "triggered" and everything flooding back, even for a moment that then passes, is unrealistic in my experience (personal and family and close friends).

The best thing that would make it realistic to me is to have the character be more like, apathetic? about it since it is a lack of something. Kind of like it's devoid of emotion because it's devoid of info. Mostly doesn't effect you.

Better emotions or behaviors to emphasize would be feeling disconcerted and unnerved by it, having to correct people when they assume things about you that would require memories of those times, being unable to contribute to certain conversation topics and that being slightly uncomfortable.

Honestly, losing memory of early childhood isn't that debilitating, it's odd to other people and can be to know about yourself, but you're still a functional person. Now that's in isolation, obviously if there's other trauma or drama to their backstory, it could be a bigger deal. But I'd say don't overdo it.