Steps to reproduce the problem:
1. Get an iPhone with latest released software.  
2. Go to test chatbox application that Disables the refresh icon using the overscroll behavior.  https://ebidel.github.io/demos/chatbox.html
3. Pull down to refresh. 

What is the expected behavior?
The pull to refresh should be controlled by the css overscroll behaviour to disable the refresh as documented here: https://developers.google.com/web/updates/2017/11/overscroll-behavior#disableglow 
Using an iPad with Chrome and the same software versions does work as expected.  It is only iPhone that has the issue.

What went wrong?
The iPhone using Chrome displays the refresh icon and refreshes the page regardless of the CSS options.  

Did this work before? Yes Chrome Versions prior to 63.

Does this work in other browsers? Yes

Chrome version: 66.0.3359.122  Channel: stable
OS Version: 11.3.1
Flash Version: 

This was initially a problem in our app that uses Sencha Touch JS framework.  The list views are drawn from JS and not in DOM.  So when you pull up to go up a list it would refresh the browser instead of going up to the top of the list.