> all the signals from the offline files in mere seconds

That sounds unlikely unless those machines had access to crazy disk I/O. A local RAID 5/10 with 8 drives would still take 30-50 minutes just to read that much data. Even with a mid-range SAN you still would have spent 15-25 minutes just reading data. This assumes 7.2K SAS/SATA since SSD/NVMe were not ubiquitous in 2015, but even with 2015-era SSDs you're still looking at half that much time spent reading.