I've tried finding statistics on the results of competitive armageddon games played at a high level (say, GM level), but to no avail. Evidently, these statistics must exist, as for example FIDE changed the time controls in the official rules from 6 minutes-5 minutes to 5 minutes-4 minutes in preparation for the Carlsen-Karjakin WC match (thus indicating that they felt that 6-5 gave black too much of an advantage compared to 5-4).

Basically, does white really have a ~50% win rate in GM-level armageddon chess games?