I feel that they slightly overestimate for me. Although, I'm never quite sure if the prediction is for perfect conditions on a flat route.
Another thing to keep in mind is that watches uses track further distance then the actual course. My fastest official (parkrun) 5k time is around 22:10. Garmin logged the 5k time as 21:xx as it had tracked around 5.1km. This was closer to my Garmin prediction of 21:45
It's pretty crazy that "Reddit refused to define the term “accessibility-focused app”. How are they going to determine which apps have free API access without this definition!?