In the simplification, the query appears to fail, however if you execute it, it actually does work, provided there is input in TextSearchBox1.Text. Note, this is not required when StartsWith(…) is the only condition.
Now, this can be overcome but at a much higher level of complexity in the query by using IF and IsBlank.
This appears to work perfectly on the surface, albeit with more complexity, however, once you add IF and IsBlank, the item gallery visibility is decreased back to 500 items. You can no longer scroll to see items past 500.
It may be considered that seeing items beyond 500 is insignificant, however from a user’s perspective, if you scroll or sort the list and items are missing, this is definitely major.
So what is it that I am not considering? How might we filter using StartsWith on multiple conditions, while maintaining the ability to see beyond 500 items in the gallery?