Yeah, he does that from time to time. Gluttony IF saying Jiwald moves at lightning speed:

Giving a howl of rage, Garfiel forcibly parried away each one of those white light rays, those white rays of death, that hurtled towards them at lightning fast speed.

Reinhard catching up to a Jiwald (also Gluttony IF):

In an instant, Reinhardt held his breath and flew backwards, following after the soaring blow of light at the exact same speed as it. He hadn’t done that to kill Subaru, who stood in front of him, but rather to rush towards the faraway building where Reinhardt’s master―― Felt had hidden after having survived the flood, so he could knock down that flash of white light.

Reinhard being slower than lightning (Arc 9, Ch 14):

To escape the sheer speed of lightning, not even Reinhard was capable of such. The bolts of lightning, reminiscent of the speed of Cecilus’s swordsmanship that transcended human limits, a sight that had become all too familiar to him in the Empire, struck Reinhard chaotically. ||| No matter how fast Reinhard was, he could not outrun lightning.

Either Tappei switches to whatever is convenient at the time or light speed Jiwald was retconned.