It is a table stakes expectation for most servers that they will not lose data when the power goes out, or when the kernel panics, or when the server itself crashes or runs out of memory. If your software requires graceful shutdown, that seems to imply that it will lose data in all those cases.

You can perhaps use graceful shutdown to perform some optimization that allows subsequent startup to go faster, e.g. put things in a clean state that avoids the need for a recovery pass on the next startup... but these days with good journaling techniques "recovery" is generally very fast. When that's the case, it's arguably better to always perform non-graceful shutdown to make sure you are actually testing your recovery code, otherwise it might turn out not to work when you need it.

So yeah, I agree with SoftTalker. Assume all shutdowns will be sudden and unexpected, and design your code to cope with that.