My understanding of how it works (I haven't reviewed the code, just going by experience)
If the MAP is less than the "Fuelcut below" then fuel is cut. Not affected by RPM at all, this is just across the board.
If the RPM is above Fuelcut RPM and TPS is below "Idle Threshold" then fuel is cut
If the RPM is below Fuel Resume RPM, fuel is normal.
From my experience, it usually doesn't work well to have fuelresume be less than 1800. Usually I set it around 2000-2100. It very much depends on how fast the engine slows down. The faster it slows down, the higher you need fuelresume to catch the idle in time.
There's nothing in the change log between 1.2.31 and 1.2.38 regarding overrun fuel cut, so if you can get a log with both firmware versions and make a detailed report in the wiki about it, someone will look at it and either explain the difference, or find/fix a bug.