Well, YMMV... A long time ago I took a taxi in Beijing (this was way before Uber was even thought of though). When we stopped at my destination the driver quickly unplugged the meter and then asked me for twice what it said. I knew this because I was traveling on a shoestring and wanted to know how fast the meter went for future reference so I had been looking very carefully at it. Maybe I was just unlucky...
The particular scam you mention is impossible with an Uber-like platform, as payment is made via the app, and there's no way for the driver to massively increase the fare in the last moments of a ride.
"Well, YMMV"
No, your mileage cannot vary, because it's tracked in the app.
I wondered why, but I guess it's to reassure riders that they're not cheating.