They are probably the type of cavities that are most subjective as to when to fill them. Some doctors fill them at any sign that there is a cavity there. Some wait on those and only fill if it seems they’ve gotten really deep.

With those the argument is not so much if they need to be filled it’s more when they need to be filled. They progress very slowly so can be watched for a while. Imo filling them earlier is always better because then we don’t have to worry about them getting deeper and once they are filled they pretty much never have any more issues.

With those it’s tough because you don’t know how deep they go until you clean them out. I used to watch them a lot but have been burned too many times with them being way deeper than they looked. Always better to fill early than later on those imo.