yes, when the option is OFF you can't select single handle (or more) and when option is ON you can't deselect handles and keyframes (to keep selected only single handle)

I cannot reproduce this. I can select handles when I set the keymap option to include handles.

The issue I have is different, but somehow related: When you select ONLY the parent Graph point, one of the handles is stuck if you try and move it.

In T64303#674236, @William Reynish (billreynish) wrote:

I cannot reproduce this. I can select handles when I set the keymap option to include handles.

Here is a GIF -

You need to alter the keymap. There is an option in the box select operator to detect handles or not. It’s off by default. So that part is not a bug.

But we can’t enable it currently because it exposes a different bug, as described above.

oh, didn't know that, with include handles it works fine for me. What is parent Graph point?

But if you enable that and only select the main point, not the handles, and try to move it, you get an issue where one handle is stuck.

Not critical at all. The goal is to select just two (or more) e.g. right side handles of two keyframes on different fcurves of specific bone on current frame and than e.g. scale them to zero so both handles had a same position. It allows you to get correct motion without any weird pops or something

To be honest, I'm not familiar with the transform operator code at all. Searching through it I found a comment mentioning a similar 'one handle stuck' problem (seemingly with curve objects), and some kind of hack to avoid that in that case.

I can't reproduce this. Box select works fine for me.