There's nothing sneaky about it at all Martin and there's no trick - far from it
John's auction is automated and has been for around a couple of decades - it's run by the software
If a couple of people are bidding against each other, the auction automatically extends for blocks of two minutes until there's a winner
It's pretty standard for how auction houses work all over the world - i.e. the auction goes on until there's the highest winning bid - just like Sotheby's etc.
Suggest you read the "How the auction works" section on the Raresoulman website here:
https://www.raresoulman.co.uk/how-auction-works/
Give that a read and you'll be better informed
Cheers
Richard