SAEM protocol version

SAEM-PDU-Descriptions.asn (https://forge.etsi.org/rep/ITS/asn1/saem_ts104091/-/raw/v2.1.1/SAEM-PDU-Descriptions.asn) says "protocolVersion (2)" but ETSI TS 104 091 V2.1.1_0.0.54 (2025-1009) [draft] says "The protocolVersion component of the header shall be set to value "1" for the present document"

Not sure why version change to "2" is required?