Accepting the need for a delay as described in previous answers, there may have been a particular reason for choosing 11 am (on the 11th day of the 11th month) rather than another time.
In German culture the pre-Advent carnival season traditionally starts at 11.11 am on the 11th of November (St. Martin's Day). In many towns and cities the mayor temporarily hands over the keys to a group of ordinary citizens. Work stops and the rest of the day is spent merry-making.
St. Martin was himself a reluctant soldier who gave up his military career.
What might be the relevance of this? The attitude of the German people was uncertain. They were unprepared for defeat. Was the choice of 11 am intended to resonate psycholgically with the German people? It was time, now, to cease from war and to give up their military work. The Kaiser had already abdicated on November 9th, though news was slow. The armistice time and date symbolically handed over the keys to the German people.
The Goethe Institute, describes the carnival and the date of 11th November. Negotiators must have been aware of the significance of the 11s. I have no evidence it played any part in the choice of time, but it may have been a factor intended psychologically to influence the German people to accept an unpopular end to the war.