After some further testing (a LOT more testing ) I seem to have discovered that the Add Filter is persnickety about its arguments when they are logically connected.
For example, I am currently adding a filter with a SubStr on the HealthState item [[(Item.HealthState).substr(0,7)=='Healthy']], which works when I add the filter when clicking on a button. But, it does NOT work when I try to use the SubStr when I add the filter OnPageLoad.
I got the data to show up in my repeater when I switched to filtering a different column and using an exact '==' match with a single word (also with a longer string that included spaces).
However, the filter in the screenshot in my prior post (on the HealthState column) did NOT work with an exact match. The best I can figure is that there must be some special character in the string 'Healthy – General' that is not matching, even though I copied it directly from the repeater.
There may be a bug when Add Filter tries to process more complex, logically connected arguments.