I think the O's made the smart decision. DL Hall has the stuff, he needs to build his confidence and learn MLB hitters weaknesses. Minors is not like MLB as everyone knows.
Very simple answer: Pride. Lyles felt he is a much superior pitcher than Arozarena is a hitter. Earl Weaver believed never let their best hitter beat you. Walk him pitch to the next hitter.
I want the O's to be like Earl Weaver's teams. They were a extremely smart teams and organization. I hope these O's will achieve that goal. I feel the O's are heading in that direction. Not much luck, more skill and intelligence than luck.