I have sent a message to support, waiting to hear back.
You are correct, indeed they are S-trig switch triggers and as I mentioned, my Cirklon sequencer has no problem - its the Keystep and Keystep pro that have this issue.
I don't need or want to spend more money on special cables - I would just hope that the S-trig outputs work as advertised on the Keystep Pro.
Thanks Edouard, lets see what support comes back with.