execution sequence of parallel execution plan
According to the quoted text Oracle will only have two parallel active per data flow operation. Take a look at the TQ column of the EXPLAIN PLAN. There is only one data flow operation for this query (Q1). There are five different parallel slave sets for Q1:

Q1,00
Q1,01
Q1,02
Q1,03
Q1,04


Q1,00 and Q1,01 will be processed first. The operation on line 7 (FTS on T3) has a slave set of Q1,02 so it can only start after Q1,00 or Q1,01 finish and free up a slave set.