New stroke per side, can you add rounded caps to that stroke?

When I use the new stroke per side I can not seem to access the end cap style dropdown in advanced. Its there but its greyed out. Is this a current limitation of the new feature? For example add a text box then put that in an autolayout frame, add a single stroke to the left around 8px then try and add the rounded caps. Does this work for anyone?

You can’t do it because this feature is equivalent to css borders which don’t provide a similar property. If you want a rounded end cap it would have to be a frame/rectangle with border-radius or a vector path.