Thanks for posting. Please be aware that there is a gradual roll out of reduced speed limits on Abingdon roads (i.e. 30 down to 20, 40 down to 30 etc) as is the case in many Oxfordshire towns and villages.
Reference can be found here, which shows that these changes, if not already live, are coming soon. I am aware that many of the residential roads are already down to 20mph. It’s unfortunately impossible to match the “go live” in Waze precisely with when it happens on the ground.