Wartime demand erased the limited role imagined for Ryūjō. With larger decks unavailable, commanders used the smaller ship as a fleet carrier despite its reduced air group, protection, and damage tolerance. Cruiser armament would have created the equivalent pressure on an American hybrid, pulling it into surface action that interfered with or destroyed its aviation capability. Japan at least produced an imperfect carrier before the treaty opening closed. The American effort to fit every role into 10,000 tons left it without a useful small carrier during that window.
Notable Point · 49:42-50:58
Why small carriers were pushed into fleet-carrier work
When no larger flight deck was available, a small carrier was likely to receive fleet-carrier missions beyond its air-group and survivability limits. A gun-heavy hybrid faced similar pressure to fight as a cruiser.