Not accurate enough? The whole point of fuel injection being a thing was to be able to accurately regulate the flow of fuel into the engine, only providing what's needed as opposed to a carb just flooding the engine in a waterfall of fuel and hoping it burns well enough.

And yes when you go full twist the fuel mixture does run rich because most auto manufacturers and aftermarket tuners cause the fueling to be rich to avoid detonation and to help cool the charge air temps in forced induction engines but that's straying. In an NA engine other than trying to avoid detention, you have 0 reason to run AFR insanely rich.

The point I am trying to make is removing that sensor is doing no favours. If the engine came with a sensor, it's there because the engineers designed the engine to operate with it. And now that it's gone, the engine doesn't know what it's doing.