sysUpTime shows the time when the snmp agent is enabled and not the system time.

  leaf sysUpTime {
    type yang:timeticks;

But can we change this configuration in order to appear the equipment sysUpTime and not only the SNMP uptime?

      leaf sysUpTime {
        type yang:timeticks;
         "The time (in hundredths of a second) since the
          network management portion of the system was last
        smiv2:max-access "read-only";
        smiv2:oid "";

sysUpTime is read-only “config false” status data (not configurable). And, it is unlikely that the equipment you refer to has some proprietary config elsewhere to change the behavior.
However, that is a question for the forum of the equipment.

Also note that the YANG model and the described behavior of the sysUpTime YANG leaf originates from a standard IETF RFC SNMP MIB. RFC 3418: Management Information Base (MIB) for the Simple Network Management Protocol (SNMP)