You can increase the duration of a match by using the /settimelimit command. It works like you expect it to work. Except, the end music will start when the default timelimit expires.
Example: see repro steps
270.8725 and for years now...
Create a private match. The timelimit will have its value according to the map. Let's assume it is 25 minutes. Use /settimelimit 40. The match will last 40 minutes, but the end music will start after 24:10 minutes and last until the 40 minutes.
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