Someone, somewhere at that company chose to hire someone... and they know what they want them to do. Why aren't they telling me?
Here I am sitting down expecting to divulge all sorts of things / do a dance, but they can't tell me what they want...
There's all sorts of reasons to not tell anyone / corporate circumstances, but it's a really bad foot to start off with / makes me worry.
And when that new person asks what they will be doing, the answer actually is, honestly, sort of ambiguous.
It's not a great sign for how organized they are, but it's still a realistic way someone could both be hiring and not know exactly what the new person's day to day will be like.
For me "we've got like 20 things going on, here's a little about them, so that kinda stuff, but I've no idea day to day how it will play out" is actually plenty honest if that's the case.
This isn't necessarily true. As a counter example, I've seen team leads who claim they need to hire more engineers in order to keep up with workload. In reality, it's a process issue, but why put in the hard work of streamlining company operations, when they can just request more people underneath them. Not only is it less effort, but they also get to say "I grew the team 2x and now manage y people" which in turn increases their compensation.
It's a case of poorly aligned incentives: managers are supposed to do more with less, but their compensation structure rewards the opposite.