Create a new document and add a table.
Goto Table Formats and apply e.g. default format. Double click to edit Table Format.
In the frame section on the left side give the frame a colour and click on the stroke dropdown. Give the stroke a width of e.g. 4pt.
Click on 'Align Stroke to Inside' and the stroke aligns inside.
Finally change stroke width to a different value > the stroke alignment resets to 'Centre'.
I tried this in the latest beta and in the release version (see signature). Both behave the same. I tried this in other stroke panels and there it seemed to work fine.
d.