The proximity principle used as a frame works correctly when there are at least two or three elements generating the container virtual limits:
It works more as a closure law:
Or the content has a central visual axis strong enough to lead to interpret it as a single element:
Following this, the top text is perfect because there are four delimiting elements ...
I never saw a rule for it and I believe is very difficult to create a rule for it because depends on the design, the fonts, the colours and the type information that you are showing there.
If you just have graphics with no legend, spaces should be enough to separate
If you just have tables they will auto separate because of design but if your ...