OK - think we got a fix for this.
Only the initial pre-population of schedules that runs after the rates have been published, will populate the below-threshold slots.
This basically means any changes you make to your schedule after around 16:35 (second run after rate publish, in case of rates being delayed), should remain as is.
The population that runs at 22:40 and 23:40 will only populate Active charge windows for which no slots have been selected (yet), and will not auto-populate slots below your specified threshold.
Deployed in fix 549.
And thanks for bearing with us. Your support is much appreciated.