I am using this example that has nested page-router-outlets. I discovered that the nested router will always take 100% percent of the page height on iOS, while on Android it will obey what you tell it.
For example, if you did something like this the nested page-router-outlet will be the full height on iOS but on Android it will actually be 400 tall
<GridLayout rows="400, *">
<GridLayout row="0">
<page-router-outlet></page-router-outlet>
</GridLayout>
<GridLayout row="1">
<Label text="Some other content"></Label>
</GridLayout>
</GridLayout>
It is working perfectly fine on ios well. There may be some other issue with your code only. As suggested by you, I have cloned the github code and added that to playground for your to test. You can access the playground from here.
What I would suggest is to add your child in above playground and test. May be that child component has 100% height that would be overlapping the parent.