Yes, the animation clearly shows that the semi-annual is due to alternate heating of the 30N and 30S equinoxes as a year progresses.

Staring at the equator vertical, one can see the higher velocity winds move downward in altitude and then flip direction. That is what is thought to be one of the forcing drivers for ENSO. Also alternating "tongues" coming from the north and south latitudes are clearly seen at sea level , and these winds have a strong annual frequency component.

I can't pick up a strict biennial period from the animation, but only the quasi-biennial. If the QBO is 28 months, that makes the period 2.33=7/3 years, and so the beat frequency when an annual cycle would constructively interfere with a QBO cycle would be once every 7 years. In other words, there would be 3 full QBO cycles in every 7 annual cycles.