Author must not have worked in enterprise software before.

That's a classic trick where the developer will push back on the bug author and say "I can't reproduce this, can you verify it with the latest version?" without actually doing anything. And if it doesn't get confirmed then they can close it as User Error or Not Reproducible.

Of course, the only way to counter this is by saying "Yes I verified it" without actually verifying it.

I totally understand that from the perspective of individual employees: they have little incentive to do more than the bare minimum to close tickets. But this behavior is typically a symptom of broken corporate culture and failure to align internal metrics. For every customer who takes the trouble to submit a formal bug report there are likely many others who just live with it, and badmouth you to other customers. Doing deep investigations of even minor bug reports also tends to expose other, more serious latent bugs. And root cause analysis allows you to create closed-loop solutions to prevent similar future bugs.

Large monopolistic tech companies like Apple and Microsoft can afford to ignore this stuff for years because there are few realistic alternatives. But longer term eventually a disruptive competitor comes along who takes product quality and customer service more seriously.

There's also going to be mountains of bugs resulting from cosmic rays hitting the computer, defective ram chips, weird modifications of the system the reporter hasn't mentioned.

You could sink an infinite amount of time investigating and find nothing. At some point you have to cut off the time investment when only one person has reported it and no devs have been able to reproduce it.