1) only toys should be allowed to be without a supervisor
2) when a built-in supervisor is available, it is (usually) good enough for everything bit the most critical applications.
3) if anything failing in your project can cause harm, a high qoualty external supervisor should be mandatory.

A hypothetical analysis
with RC reset you may fail starting - and WILL fail on brownouts - so the user may have to restart one of 50 times. No big deal for a toy, but totally unaccepatble for anything else.
With an internal supervisor you may fail a start or brownout one case in 5000, acceptable in most cases where life and limb is not at risk.

Erik