I don’t know that the truncation design is “arbitrary” – it might be intended to strike a balance between usability and readability. The thinking here is probably that very long titles might make Charts less useful. Since Charts can show note $Name for all levels of an outline, a Chart with lots of long $Names could be difficult to read and navigate. In other views, and in the Text panel, long names are truncated.
One approach to ameliorate this, is to make your HoverExpression in your notes’ prototype(s) simply
$Name
And the whole $Name will appear when you hover over that note in your Charts.
