XLS IR Visualizer falsely highlights edges that are not on the critical path

In some designs in the IR visualizer (https://google.github.io/xls/ir_visualization/), when critical path highlighting is selected, sometimes edges that are clearly not on the critical path get highlighted. This seems to occur when there is a critical path
```
A -> B -> C -> D -> E -> F
```
but there also happens to be an edge for example
```
B -> E
```
It seems that the rule is to highlight an edge whenever both its source and its destination are on the critical path. This makes sense, but leads to non-critical edges such as `B -> E` getting highlighted.