OK, I figured this out. Turns out my Arduino [Partition Scheme] setting was incorrect. I had a setting of
[Default 4MB with spiffs (1.2MB APP/1.5mn SPIFFS]
instead of....
[8M with spiffs (3MB APP/1.5MB SPIFFs]
Now after the sketch upload, I get
Sketch uses 1265261 bytes (37%) of program storage space. Maximum is 3342336 bytes.