Until the block rewards subsidy goes away, an empty block still technically has one transaction: the coinbase which distributes the generated coins from the block reward.
So, while it isn't adding any value by including other transactions, it does, indeed technically fit the definition of mining.
Every single definition of mining states "transactions", plural. Nothing is confirmed in an empty block, it does not meet the definition. Seems to me the empty block thing is a huge oversight, and that empty blocks should not be valid and the network should reject them. The only block that should have been considered valid with a single transaction generating coins was the genesis block.
Has there been any analysis of an "empty block attack"? Imagine what would happen if an inordinate number of empty blocks were solved and submitted in succession? Bitcoin would effectively cease functioning.