Ionic v4.0.0-rc.0: problem ios css

Using Ionic v4.0.0-rc.0 I tried to generate a starting project with a simple tabbed interface.
Without further changes, I tried the application on an iPhone 6s (ios 10.0.2) with Google Chrome (v71.0.3578.89) and I found problems related to the css:the toolbar buttons are vertically aligned and overlap with the contents of the tab (see attached image). Is it a known problem?