Entities are no longer knocked back instantly after taking damage

In earlier versions, the instant an entity was damaged, it would start moving. However, in modern versions, there appears to be around half a second where an entity remains standing exactly where it was before motion starts, despite it correctly turning red instantly.

Attached videos are from 1.2.5, 1.3.1 and 26.2.

Expected results: as soon as an entity is damaged, its motion should begin, exactly at the same time it turns red.

Actual results: we see this happening as expected in 1.2.5. However, in 26.2, despite instantly turning red upon receiving damage, there is usually half a second where it stays exactly put.