So what you means is it's possible, just not the way you thought or wanted to, and the tool works just fine. Gotcha.
If the tool provides the switches on the cli, and the cli cannot do the task which is possible not using the cli. Then the cli is broken. That's not a difficult thought to hold in your head.
The tool defines how to use itself. If it requires using a temporary files to bypass shell limitations that it has no control over, then that's how it should be done and not a broken behavior.
"I want to use blue and red on my multicolor pen at the same time and it's not working so clearly the pen is broken might fit in your head but the pen still isn't the problem...
If you could actually read and study those two solutions, you could notice that the grok has moved that stuff into separate file.