Actually this is great feedback and you are correct. If those 4 elements were children of an artboard then you would be able to use the align commands. We should carry this over to groups as well when feasible. By that I mean, a group's bounds are derived from the bounds of its immediate children. So if you for example only have 2 elements in a group you wouldn't be able to align them relative to the group, else the groups bounds would change. But in your case with the button or label they should allow the same alignment functionality.
For now you know the two lorem ipsum text labels are defining the "width" of the group so you can easily just select both of those, and either the button or the heading, and use the "distribute" button (last button on the left group of alignment buttons). Let me know if I wasn't clear.
I recommend adding a feature request here for the group relative alignment functionality you seek. Adobe XD Feedback : Feature Requests & Bugs