Currently, the block generator signs the block header and transactions (bytes of block headers and all transactions in it).
The feature of signing only the block header by mining node has been added to version 1.2.0 of the node. This feature is enabled with the activation of the "VRF and Protobuf" functionality (No. 15) on the node. Version 1.2.x is currently available on stagenet.
To provide the mentioned feature, MerkleRootHash of the block transactions is added to the header to prove the integrity of transactions in the block. This allows you to verify the block header apart from transactions, which makes it possible to provide evidence of the presence of transactions in the block without the presence of all transactions.