This discussion is forgetting calibration. The battery pack also needs to go to 100% to calibrate the curve.
Maybe this will make it clearer... this is my current understanding, open to corrections.
Voltage curve: this is how the voltage of the pack varies with state of charge. NMC has quite a strong curve so a full battery will output a considerably higher voltage than an empty one. LFP has an almost flat curve by comparison (except at the extremes).
Balancing: balancing the individual cells in the battery to equalise their voltage. This is important so that individual cells are not over or under charged as the whole pack is charged and discharged. Since NMC has a big voltage change with state of curve and big buffers it is easy for the BMS to keep track and balancing is not needed regularly, monthly is sufficient. LFP needs this more often because the voltage changes are much smaller and harder to keep track of, so weekly is typical. Balancing can occur at any state of charge but is easiest at max charge due to the curves.
Buffers: there are top and bottom buffers which are spare battery capacity to avoid overcharging and overdischarging which can damage the battery. NMC makes good use of these (eg MG4 LR has 64kWh but only 61kWh usable - 0% to 100%). LFP has an almost flat charge curve by comparison and has a very small buffer (low risk of damage). This is why LFP balancing only takes a few watts, but NMC much more.
Calibration: as the battery pack ages the cells slowly degrade and can hold less, the BMS needs to see a wide range of charge states in order to calibrate the battery as it ages. This is why we have the 10%-100% every few months recommendation.
Advising people to charge LFP to 100% at least weekly achieves calibration and balancing, so is an easy thing to promote.
With NMC, again due to the curve and chemistry, staying at high states of charge will lead to some battery aging, hence it is worth asking people to charge to 80% normally and 100% monthly to maximise their battery life.
However, unless you keep your car for years and years, you may as well just use it as you'd like to.