The traps are a short ROM muscle, and like most other short ROM muscles are very powerful. If more serious work would be directed to the traps, than most men would be able to shrug the same, but usually more than they DL. Hence the suggestion to shrug at the top position of DL's, adding to the attempt to complete a total compound back workout. The whole chain of back muscles (calves, hams, hips, glutes and up to the neck) are getting strengthen by that short range extra work load, reflecting to the improved dl it's self.
Taking a bar (about mid-thigh) from a PR/supports/platform, etc., try preforming shrugs for 2-3 sets of 6-12 reps. The may surprised how the poundage advances rather quickly from workout to workout. Changing the grip from the usual middle to extra wide, touching the inside collars of the bar, to a narrow grip, where the thumbs are around 6" apart can make a notable different on results...both in muscle size and strength. Some will alternate grips in the same shrugging routine. Some from workout to workout. Feel free to use straps for heavier loads. Why limit the powerful potential, and size, of the traps and upper back when a grip is the weakest link. The grip will usually catch up with the heavier weights after awhile.
For most men the better grip position for shrugging (and DL'ing) would be with the thumbs facing forward (hammer grip style). Though obtaining enough plates on the bar, after a while can be limiting for either shrugs or DL's. For pure bb'ers , a trap'shrug bar may fit their needs quite well.
There are also overhead BB shrugs, a very overlooked exercise for a complete trap and shoulder girdle movement. Just press a bar overhead, locking the elbows a bit, and shrug A whole different feel to the exercise and can build power very well. Adjust difference grip positions, also. from extra wide (inside collar) to middle grip. Any version of overhead shrugs will hit the total three delt heads.
Good luck.