Of all of the possible subjects that the Polymath could bring up during the meeting, Mr. S. was one of the worst possible outcomes for Ves.
Mr. S. did not exist as a literal human mech designer and individual. It was a false identity and smokescreen that Ves used to fend off the curiosity of mechers such as Master Moira Willix and the Polymath herself.
Ves had always been afraid that these incredibly clever and powerful figures would figure out the truth one day.
There was no Mr. S.
They had been deceived by Ves all this time.
If there was anyone who best fit the label of this mysterious and illusionary mech designer, it was either the Mech Designer System or Ves himself!
The only advantage that Ves could rely upon to maintain the increasingly elaborate facade that he set up was to use his time travel shenanigans to paint the illusion that Mr. S. was an old geezer who had made his presence felt throughout history.