Take a look at the screenshot. The first shown change is marked with an ! but does not have any background color. Niether does the following group of changes but each change in the group has it. This makes it more difficult to spot bad changes and makes the highlighting concept slightly useless in enhanced changes.
So this has already been reported at T146291: Recent changes page: ORES scored entries are not highlighted when 'Enhanced recent changes' option is used where you can also find screenshots. As you are working on this, could you decide which way they should be merged?