.cast dist #spellid [#dist [triggered]]
Did you specify dist value? If not the spell is cast at 0 distance from you, meaning it's centered at you.
I've tested with ".cast dist 26573 20" on Mangos One and worked perfectly. Its ChatHandler::HandleCastCommand in src/game/ChatCommands/Level3.cpp is identical to Mangos Zero so there should be no difference.