Thanks, @awesomeonion, for the explanation. I suspected that the player had been rolled back but couldn't guess at why that may have been.
So trade offs, in the form of unorganized random thoughts...
Personally, I only use Hopscotch and the forum from mobile devices that have Hopscotch installed. So I prefer project links to open in the app. Though, the business incentive is obvious enough for a high quality web player. How the app player works isn't so revelant to me as how well it works.
The Whomp bug was never too big of a headache for me. Just press edit / play again...
Loosing numerous bug fixes would be unfortunate, but recoverable if you're willing to make the investment.
Would the player used be based on the project version? Regression without re-fixing the bugs would likely cause some published projects not to work right.
Personally, I would like to see the focus be on providing a bug free, high performance (i.e. low lag), high integrity (i.e. no data loss) app in whatever direction that takes you.