Baptiste Mathus I disagree that is sensible behaviour. Why just remove the next build? What not all queued builds? The feature is "Disable" not "Disable and Purge", there is already a dedicated option for purging a job's build queue.
In general, I think the queue should not be touched when disabling a job. From experience, I may need to temporarily disable a job to prevent new builds from being triggered, fix a bug in the job's configuration, and then resume the queue.
I'm working on some improvements to GitHub Branch Source, so I don't currently have the time to work on a fix. Either way, the bug needs to be reported.