From the BBC website*
(sentences reordered for clarity, because the BBC correspondents can't write for sh!t these days )The Uxbridge and South Ruislip MP's legal team argued that the offence of misconduct in public office was about the secret abuse of power and there was nothing secret about Mr Johnson's claim, which they said had been challenged during the campaign.
Mr Darbishire said the attempt to prosecute Mr Johnson was "politically motivated and vexatious".
Addressing Mr Johnson's barrister, Adrian Darbishire QC, Lady Justice Rafferty said: "We are persuaded, Mr Darbishire, so you succeed, and the relief that we grant is the quashing of the summonses."
My understanding from this is that it is quite possible that there was no case to answer, so the issue of Boris's honesty may have been irrelevant.
*https://www.bbc.com/news/uk-politics-48554853