This change is vital because version 3 transactions include inheritance rules that allow for concurrent spending, similar to how TxB2 operates. The specification draft in question addresses these and possibly other related changes and can be reviewed in greater detail through the provided GitHub link.

The adoption of version 3 for HTLC-X transactions is an important step towards improving the network's efficiency and reliability. The inherent inheritance rules will enable more seamless transaction processes which are crucial for the network's scalability and user experience. As such, this update represents a significant technical enhancement for those involved with developing and maintaining the system as outlined in the spec draft.