Currently `kdumpctl estimate` is based on a hardcoded formula which is based on experience, and calculation based on kernel and initramfs static size. This is incapable of covering all real usage. eg. when a kernel module or userspace program consumes a lot of runtime memory, `kdumpctl estimate` will not provide a reliable value. A better approach is being worked upstream. `kdumpctl` will trigger a real kernel panic and collect memory usage during the kernel panic dump process. The collected info can help provide a much more reliable memory usage info.
After evaluating this issue, there are no plans to address it further or fix it in an upcoming release. Therefore, it is being closed. If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.