Two weeks ago.. I was traveling on AA award ticket (sorry No UA).
ATL-DFW-YYZ
Weather delay in DFW of my first flight. Missed my connection (last flight of the day).
AA was willing to give me AC nonstop(next morning 6am) / UA connection (next morning). But I choose AA to ORD on same night and AA ORD-YYZ next day. Spent the night in Chicago with my family.
AA treated me the same. No mention about award ticket. Maybe AA has different rules.