Yes. The Fujifilm GFX 100s II together with the Fujinon GF 500/5.6 OIS can indeed follow focus on fast moving subjects. I tested this with bikers who fast zoomed by.

I had AF-C enabled, as well Eye-AI, and placed a larger AF box into the upper part of the frame. The shutter type was "Shutter EF"; which means electronic first curtain shutter (EFCS) which ends with a mechanical shutter that ends the exposure.

I did not enable fast shooting (several frames per second).

The mans face is razor sharp

down to the very wrinkles visible, as well single hair. Despite him having a fast speed on his bike (i followed him along his biking path) with a shutter speed of 1/1250 sec.

So no, the GFX + lens can do fast photography - with tips and tricks. It isn't as sluggish as it might been suggested by various reviewers. However, I am sure there is struggle in certain situations. Such as when a person comes straight towards you, being relatively close. Here the AF might fail sometimes.

Now that being said - it isn't my typical type of photography, as i am often a slow photographer. Yet, it is fun to test the thing i almost never used before. Now doing all this with a 102 MP camera, is nothing but crazy. But it works.

I am a very, very happy guy about it.

Animals i have not yet tested with the Fujinon GF 500/5.6 OIS lens and special camera settings.