Just to illustrate my point with flamed wood here is a very quick and rough sketch of two planks of wood.

On the top plank the grain runs nicely through the whole length of the plank. In reality this does not allways occur and there is usually some curve or runout in the grain because trees twist as they grow. but it is what we should aim for with neck wood
the plank on the bottom shows a flamed piece. Flamed wood has wavy grain, i didnt bother to draw it all but you can see that not all the grain stays within the borders of plank. This means there will be less grain running the whole length of the neck and more potential weakspots/flexability.
On the peice i drew most of the grain would still be running the length of the neck and it would probably work fine but would not be as stiff as the top peice - like yours i assume.
On more figured woods (imagine a PRS style quilt) the grain would almost be zig-zagging down the whole length of the board and it would have almost no longitudinal strength because there would be no grain that ran the whole length of the plank, it would be be completely unsuitable for a neck.
Its a bit of a simplified explanation but i just wanted to try and explain something about wood choice when making necks. Obviously it all depends on the actual peice of wood because they are all different
I remember reading a little story about our facination with figured wood instruments a few years back... not sure how true it is but here goes.
Our facination wiith flamed maple on instruments goes back to desirable violins by people like stradavarius. People started to associate the wood with the fantastic tones these instruments are famous for. They start to believe that these great violin makers where using very expensive figured maple for their violins, probably sawn by virgins on a full moon or something. Basically flamed maple became a sign of a quality instrument
The truth . . . violin makers used the wood they could get . . . the stradavarius story i heard suggested that he used maple from broken boat oars that had washed up on shore that the turkish had sold to the armenians (or the other way round). Due to the rivalry between the countries the turks would always try and sell the armenians the lower quality oars . . . in other words the flamed ones . . . they snapped and got washed up on shore. . . those damn economical luthiers started picking up the scr@ps to make instruments from.
Thats probably more than anyone needed to know about flamed wood so i will leave it there . . .
. . . and nobody get me started on swamp ash!!! I pay so bloody much for the stuff and only 30 years ago most wood yards would sell it cheap because its considered inferier to normal ash for most other things!!!