Note: This question does not apply to I3C Basic.
In I3C v1.1.1, Defining Byte values 0x7F and 0x55 now describe the process of configuring and enabling Data Transfer Early Termination in addition to the previously described HDR Ternary Flow Control. In the I3C v1.1 specification this was defined as ACK/NACK only for WRITE Commands, whereas it actually applies to all HDR-Ternary Commands. The new definition of HDR Ternary Flow Control clarifies the full set of features that these Defining Bytes (as Sub-Commands) configure.
Additionally, specification Section 126.96.36.199 now provides more context for these capabilities, provides a better explanation of the default state of HDR Ternary Flow Control, and defines which of the procedures defined in its sub-sections apply when HDR Ternary Flow Control is enabled vs. is disabled.