Hi Grim Reaper!
I actually have very good news for you, because none of your worries are necessary. The reason why we recommend Chrome, is that Chrome is the best Browser for HTML5. Why does that matter? Because DE05 is already running on HTML5.
We are right in the middle of switching all servers to HTML5 and will get rid of Flash entirely way before December 2020. We are getting rid of it right now
It's worth mentioning that not just Chrome will get rid of Flash, but everyone. Flash will officially not be supported anymore in 2020 anywhere. That's why we switch to HTML5, like many other games do, did or will do.
So, to answer your questions:
1) Because it's, on average, the best browser for HTML5 right now.
2) Already done. Absolutely nothing about the game itself changes, it's merely a translation of the game from Flash to HTML5. Since you apparently already played on HTML5 without even noticing, that should answer your question if anything changes