PPL studies have never involved a knowledge of commercial operations. The limitations and guidance for private flights including take-off and landing are found only by reference to the Aircraft Manual/POH. Certain performance data is not available in many aircraft manuals though, especially very early ones, but it is not a requirement to write up an operational limitation as a supplement and have it approved. Amendments to aircraft manuals particularly operating data is sometimes required by the CAA to be inserted as an amendment to the POH.
The guidance given for take off and landing in the old but still current Safety Sense leaflet, in my view, is excellent and has a particular purpose; to act as guidance when, and only when, the aircraft manual does not. The advice is always generic and can be described, at best, as putting the pilot on the safe side of wrong, however never compulsory.
I don't think there are two conflicting standards. The additional limitations imposed for commercial ops are there to deal with the sometimes intense external pressures that a commercial pilot can be subject to.