Translation:The three wise men are visiting the baby.
I guess you're saying that the redundant definite form is obligatory in Bokmål. This is clearly not the case: the above sentence is in this Bokmål course, and yet it does not have the redundancy.
It would be more accurate to say that the usual modern standard is to include it in line with the way most Norwegian dialects work (plus Nynorsk and Swedish), but that older styles which exist within Bokmål tolerate the more typically Danish construction.
Well I'm not sure whether we are talking about the same thing or not, but I was taught what I'm talking about under the name "double definite" and it consists in leaving a word in the definite form even when paired with a demonstrative adjective, as in "denne hunden". Is it this you're talking about?
Yes, kinda. We're talking about the double definite phenomenon that occurs when an adjective precedes the noun, as in de vise menn[ene]. In such sentences, the definite article at the beginning is obligatory, and the definite suffix on the noun is optional.
The use of that definite suffix is the norm in most Norwegian (and Swedish) dialects, resulting in it being the standard construction in Nynorsk, Bokmål and Swedish. However, Bokmål is Danish-influenced, and thus old-fashioned sentences may lack the definite suffix, as in Danish. This exercise is an example of that.
The double definite construction with demonstratives is basically similar to this, in Norwegian anyway.