10-2-5b allows an USC foul to offset with another USC or DBPF on the opponents , as an USC foul occurres during a play it is assumed not to have any impact on the play, itself. Sorta' like "sticks and stones will break my bones, but names will never hurt me." I proposed this rule change in 2015 and it was accepted. My problem with 'in order of occurrence enforcement' was several-fold :
(1) If matching USC/DBPF fouls occurr inside either 30, having the distance if the first flag on B wouldn't be fair.
(2) If said fouls occurred on a TD play ,OOO enforcement can provide 6 choices, too complex, even for us

,
(3) This one happened in my game once, 3/7 @ 50 :
- A1 tackled @ LOS, then DBPF by B1;
-A1 then throws ball @ B1 =USC;
OLD WAY : Told U

to put his 'walking shoes on and hike to B's 35. I'd signal #7,38, 8. Ump then does pirouette and returns to 50 where I now signal #7,,27,.8. Some may not understand why A gained a new series but the chains did't move

TODAY'S WAY : Leave ball @ 50, signal # 7,,38,27,,10 -4/10
......AND LET THE BAND PLAY ON

NOTE: YOU CAN STILL HAVE "OOO' ENFORCEMENT IF A 5-YD COUPLES WITH A 15-YD DB FOUL= Encrouchment on A, followed by DBPF on B = A gains 10 yards.
IF YOU HAVE AN UNEVEN 3 OF DB FOULS, ALL WILL BE ENFORCED + 2 DBPF on A, 1 DBPF on B = A loses 15.
Hope this helps