Now I see how the toy got shredded. They feed off of one another.
Yes, with two you will find this, and not just with Basenjis. My sister had two dogs that liked to dig in the dog run. After one had an injury they separated them so she could heal, putting her into a smaller run. Neither dog did any digging during that time, but once reunited the excavations resumed. Two will generally get up to more mischief than one, but two aren't as likely to be deliberately destructive as one with separation anxiety on its own. However, games can escalate into unintentional damage.