Reboot information is related to SNMP service/daemon. It should not be work like this. SNMP service/daemon can be crashed or restarted for some reason (most of the time). And for that it's not a reliable service for tracking reboots. We need other solution (maybe different OID) for this out of the box. There are plenty of threads about this issue. Some of them are below.
linux snmpd restart during logrotate triggers false reboot alert weekly
Better Method of Calculating Uptime
Re: Misleading SNMP Uptime information
Re: events with "...nodename REBOOTED AT...date time"
Uptime SNMP and reboot messages