People who switch from O to D or vise versa can do well because they have a good understanding of the opposing concepts, points of attack, perspectives, etc. D Washington was a high 3 star recruit, his size & athleticism is really a perfect match for OLB, in fact NB even mentions this in his presser today.
Due to Kaden P & Sam Brown being such a high quality WRs, with similar body types, I would assume D Wash seen the writing on the wall, that he would be #2. So instead of seeing a limited # of snaps on O, in time, he could be a significant contributor on Defense, in a already thin position group.
Between his athleticism, body type, understanding of offensive perspectives(How that historically bodes well for those who change positions), and our need for athletic LB's, I think its far more productive then him staying at WR. It'll obviously take him a while to learn the specifics of the position & defense schemes, patience required, but long term we'll extract more value from him this way. Which is a logical thought process, a theme you should subscribe to.
When you think of many of the great OC's or DC's in NCAA history, many of them started or played on the opposing side of the ball. Because they were exposed to the opposing methods, techniques, perspectives & philosophies, this gives them a better understanding on how to exploit them and/or predict their actions/thought processes. Same goes for players... Knowing WR techniques, setups, etc may provide a unique understanding for DW, compared to an LB whos always played Defense. Obviously time will tell how we will do at LB, but I also trust NB's evaluation on his potential & upside as an LB, and considering how thin we are at that position, if he's talented, he'll make a more positive impact at LB, then he would at WR, and I call that a win. As with every Freshmen, time will tell.
Watch his HS film, if he can hold onto that speed and gain 10-15lbs over the next yr or so, that would make for the perfect physical traits you seek in a LB, we'll see if he tunes his instincts & physicality.