Can we process binlog event and rowcopy parallel?

Review source code ,we find gh-ost process event by this rule that "We give higher priority to event processing, then secondary priority to rowcopy"

One question,this only think by performance,decrease original table's write load?

From design logic,can we process binlog event and rowcopy parallel,we have more test ,gh-ost ddl speed slower than pt,so we want to speed up.

Could you have any good idea?