That’s not how it is advertised 
- Both the FP3 and FP3+ have 64GB of memory
- FP3+ has an Upgraded speaker module
- FP3+ The core module is different and provides better audio for the updated speaker module.
- FP3+ Both camera modules are updated :: The Front from 8MPx to 16MPx and The Rear from 12MPx to 4 x12MPx Bayer
- FP3+ The rear cover is different and generally with the back cover and upgraded module housing results in 40% more recycled plastics
The FP3 is also different in that the back of the phone is transparent and it comes with a bumper