It can! But it may also mean that doubt = an uninformed or immature faith. (Children can have more mature faiths than some adults.) It’s not sinful to ask for reassurances, and God promises us trials to test our faith!
You’ve seen this before, from the end of Keller’s book:
During a dark time in her life, a woman in my congregation complained that she had prayed over and over, “God, help me find you,” but had gotten nowhere. A Christian friend suggested to her that she might change her prayer to, “God, come and find me. After all, you are the Good Shepherd who goes looking for the lost sheep.” She concluded when she was recounting this to me, “The only reason I can tell you this story is – he did.”