Make `df` stop listing TM snapshots?

Recently, df started listing over a hundred time machine backup snapshots.  I can get the previous output with df | grep -v backup but I'm wondering why the change and whether there's a better way to restore the previous behavior. Details: Until a week or two ago, df has never listed a Time machine snapshot on any Apple laptop I have owned.  This of course includes most of the nine years APFS has been in use. Starting more than a week ago, it was listing more than a hundred of them.  This behavior persisted after a reboot on 4 July.  But after a reboot on 7 July, sometimes there are none and sometimes there are two. Until the unwanted behavior started, using Finder or find or ls or cd did not cause it to happen.  Nor did it start when using the Time Machine GUI to browse or restore.  Nor did it start when an hourly backup started or ended. As can be seen in an answer and in comments, others have a significantly different experience—which is also disconcerting.