Sekiro dash animations replaces Light Weighted Roll ones. Frame data is the same for both vanilla rolls and ERTE ones, i-frame wise, but you can cancel the dash earlier into other actions or attacks, creating new combat tech like:
Side stepping
When locked on an enemy, dash to the sides to perform a Side Step that can be cancelled inmediately into other actions.
Double Dashing
You can cancel the dash into another dash earlier than with a vanilla light weighted roll.
Dash & Weapon Art chain
You can cancel the dash into any Weapon Art. This is specially useful when combined with dodging Weapon Arts, like Quickstep or Bloodhound Step, because it allows to extend the i-frames window when dodging attacks.
Weight Load feature
Similar to Weight Rate, Weight Load adds frames before being allowed to cancel into the next action. With the Sekiro dashes, the more weight load you carry, the later you will be able to cancel into another dash or action. So in order to be able to cancel the dashes as fast as possible, you have to go low weight as much as possible.