I also had that thought as a possibility. But then I figured that rather than being an effective disguise, that getup would have probably made him
even more recognizable because Barnabas wore it during the whole Collins Cannery reconstruction, which would have been big doings in town and something the whole town would have been likely to pay attention to. Even in silhouette, practically anyone in town would have probably recognized him!
So, if wearing that getup was supposed to disguise himself, Barn wasn't thinking very clearly when he made the choice. But then, on second thought, what else would really be new? Regardless of the version of DS, Barn often makes ill-considered decisions.