dotnet-suggest doesn't suggest after typing a dash or two

I was trying out dotnet-suggest, and found a very strange thing:

When I type in:

```
t-rex
```

I get suggestions. But when I type in an extra `-` or `--`, I don't get any. If I type in first letter (e.g. `--f`), I get suggestions again.

It's a very natural thing in PowerShell to type in the name of the command, then a space and a dash, and then start tabbing until you find the parameter you're looking for but can't remember the name of. This doesn't work here and it's frustrating.

Basically, I want suggestions for all these inputs:

```
t-rex
t-rex -
t-rex --
t-rex --f
```

But I only get for the 1st one, and the 4th one, and that's just so strange and confusing.