If Daniel has nyctophobia,,,

[Romulator]

Daniel's traumatic experiences within the tomb are the cause of his nyctophobia.

Was this confirmed at all or are you just making an assumption?

Isn't 'assumption' what Amnesia is?

Either way:

Young Daniel developed nyctophobia, an intense fear of the darkness. This was not because Daniel was literally afraid of the absence of light itself, but because he feared the possibility that he may be trapped forever in the dark with no hope of escape.