Interesting one this - I once arrived T4 very late from DOH and had an early morning departure from T3. Rather than hotel I took flight connections and into the T3 overnight pen. There were no issues going through transfers so late and night and in fact they put me in a little minibus to get across the airport - nobody else was going through transfers!

T3 overnight wasn’t great but the lounges opened early so shower and breakfast and I was back on my way.