Witching hour boy is a simple petty thief, alla Robin Hood, that helps the poor. Denjiro was an educated man, with a vast knowledge of both history/politics and economics. He was literally teaching the Scabbards, and controlled their funds.
Denjiro's potential surpasses that of a simple petty thief. The dude is clearly Kyoshiro. Not just that, but
he has been collecting money/resources through the Yakuza for 20 years. The Witching Hour Boy is probably someone like Hiyori.
Denjiro's potential is far too great for such a simple role that doesn't take into account (1) his knowledge of money/politics (2) his Samurai strength. The dude fought fucking Kaido and survived + he's super smart/educated.
All the Scabbards reunited, but Oda is keeping Denjiro a secret, because he's the "Witching Hour Boy"? Get fucking real. No one gives a shit about the Witching Hour Boy when we're going to take on 2 Yonko. He's clearly Kyoshiro and is going to stab Orochi in the back.