/vmfs/volumes/[datastore UUID]/vmkdump/[dumpfile identifier]-########.dumpfile
This is an expected behaivior depending on situation.
The coredump file has a recommended capacity based on the CPU and memory size of the ESXi host, and if the coredump file does not meet the requirement, it will be automatically recreated and renamed.
The renamed coredump file can be used as is.