Fits in with their strategy of almost continual harassment. They were doing the same to the Japanese earlier this year. Gives them an opportunity to test Taiwan's air defences as well.Perhaps it is some kind of Attrition game. They have more Aircraft, thus pushing Taiwan Fighters operational tempo will increase their weariness and drove potential problem. This can work either to the hard assets and also man power.
Trouble with this tactic is that it just takes one nervous new recruit and all of a sudden you have a shooting game.