PreloadEffect very slow loading

cocos2d-x C++
17

Here are some results:

Nexus 6P:
10 oggs: 0.2s
10 waves: 0.17s

Lenovo A1000L-F:
10 oggs: 0.7s
10 waves: 0.025s (wtf)

Samsung Galaxy A3 (2016):
10 oggs: 0.46s
10 waves: 5.8s (strange!)

My updated test project:
PreloadBug.zip (5.6 MB)