I think the answer is... it depends.
I believe if you are using the 622 with the flash in Manual mode, it should work because the flash is doing a simple fire at X power setting. However, if you are set to ETTL, the flash emits a pre-flash allowing the camera to detect exposure of the flash... the pre-flash will cause whatever is connected to those items to fire at that time, and it won't recycle fast enough to fire again during the exposure.
yea, tried using ETTL off-camera flash, its not for me (as its too inconsistent) so keeping it manual always when doing off-camera speedlight flash photography... So if manual, its totally fine?

