Well, let's think about it for a second (pun intended).
You want to sweep from 1 Hz to 3 Hz. Let's simplify. So you need at least one period at 1 Hz, then one transition to 2 Hz, one period at 2 Hz, then transition to 3 Hz, and one period at 3Hz.
Since one period at 1 Hz take one second, that is : 1s+1s +0,5s+0.5s +0,3s+0,3s... 3,6seconds to do move that way.
That is, if they simply jump from 1 to 2 to 3 Hz like that.
Which they don't, but they gradually stretch phase of sinewave, so 4-5 seconds minimum to make transition from 1Hz to 3 Hz sounds about right. In fact, that is quite short too, for that transition.
So minimum time of 4-5 s for that sweep is not a bug, that is just fine.
As for no 2, try setting sweep to 10 seconds to see if there are any changes there. Also try different start and stop frequencies to find what does work and what doesn't. Where exactly things break?
When dealing with things like this, you need to investigate from all sides, gather details, and make sure what you saying is right and that you can demonstrate the problem if there is any.
Many times by analyzing you end up realizing there is no bug, but sometimes things simply work differently than what you think they should. And you learned something. Also win.
OTOH, but there I see a bigger problem you didn't notice.
10 second maximum for sweep is not nearly long enough. That is a problem, exactly because of what was said above.
If you want to make a sweep in audio range from 10 Hz to 20 Khz, more appropriate time would be 100 seconds for sweep.
Regards,