Burn means different things to different people I suppose. In the case of BTS Graphene a burnt share is one that is held by the blockchain for possible release later. In BTS 1.0, and I believe most other instances, it means transferring of value to an address for which the private key is not known.
It's just semantics.
In the case of BTS Graphene the pool is drawn on to cover the costs of running the network. In BTS 1.0 where a burn is the traditional understanding the share holders would have to decide to hard fork to increase supply if the number of BTS got too low. Both scenarios result in the same thing - enough BTS to allow the protocol to exist. The difference is BTS Graphine doesn't require the hard fork.
Since the pool cannot be spent by anyone but only metered out to workers I feel it is basically burnt. It cannot be used in commerce.