For Lectora Online I believe we scale the text up. I will look into this.
We have also talked about adding configuration for dialog boxes, to adjust the look, colors, fonts, etc. It seems on mobile a dialog should fill up the screen so there is less confusion. This should also allow overrides per view.
Our workaround is to tell authors to navigate to a page. Then on the page have a close button which runs a Go to Previous Page action. Inside of a random test this may not be possible, but in general it works nicely on mobile devices.
This is written up and will be discussed more in the near future. Thanks.