"The Listener, IQ, and Azed assume solvers have a copy of Chambers."
I don't know what the Listener and Azed assume, but there is nothing printed in the i newspaper to say that Inquisitor solvers are expected to have a copy of Chambers. How are readers expected to know? I certainly didn't until I started asking about it on Fifteensquared and this forum.
And it's not like entering a Scrabble tournament. When you enter something like that you're given a copy of the competition rules. The Inquisitor is published in the i newspaper every Saturday, which anyone can pick up from their local newsagent. You don't have to submit an application or qualify for it.
I've managed to complete ten Inquisitors without a copy of Chambers, so it clearly can't be essential. Everything in Chambers is - or should be - available in some other reference work. If compilers are sourcing material from Chambers that
isn't available in any other reference work, that can only be because either Chambers is in error, or they've misunderstood what it says. Which appears to be the case here.