This is a known issue in build 9.5.0.711. If you disable Microsoft SQL logs truncation in Job properties then Microsoft Exchange logs truncation will be disabled too.
Exchange logs truncation is regulated by a single boolean when you call SetBackupSucceeded() WinAPI with Exchange VSS writer writerID.
When that boolean is set to true Exchange VSS writer goes ahead and truncates the logs, and v9.5.0.711 sets this boolean to false based on SQL configuration in Job properties.