We try not to break existing users work flows for new minor features, and since it did, it had to be changed.
We generally also do not offer preferences for every small bit of behavior, so no, sorry.
I was overjoyed that JRiver actually started using standard OS behaviors in 21.0.50
Why are you teaching users bad habits?
If it breaks users "workflows" (I've not seen anyone complain!) then make it a preference that you phase out eventually.
The way that it's behaved until now broke the workflow that millions of people are used to in other programs like Windows Explorer, Adobe Bridge, and any other application which uses thumbnails that can be resized.
Non-standard interactions like these are why people find the program difficult to use.
People shouldn't have to learn all of JRiver's idiosyncrasies.
There's a reason that every other program follows the same basic set of interactions.
Try to find another program that uses middle-click on a tab to change view, instead of using it to close the tab.
Or a program where middle-click
doesn't close the tab.
Who comes up with this stuff!?