It varies slightly visually as not all gauges read exactly the same. Hard cut is set in the ecu to 6500.
Several things about the m44:
Peak hp is 6000, going beyond that you’ll go slower, not faster.
The crank dampers have a reputation now for coming apart beyond 6500. They’re not available new and decent s/h are getting scarce. I can’t find anyone selling alloy dampers commercially anymore, so it’s Custom only.
BMW engine internals are not balanced from the factory, pistons vary +/-3.5g, rods 3-5g, doesn’t sound much but the forces acting on them are proportional to the square of the revs. If you wish to continually rev above 6K, balancing is an absolute MUST, otherwise the engine WILL go Bang.