That’s completely incorrect about pianos. I wonder where you obtained that idea. The trichord set is tuned very precisely in unison to a high degree of accuracy. I speak as a former professional piano tuner and instrument maker. On a piano octaves are always true and beatless, but due to the departure from ideal infinitely thin strings of the relatively thick steel wire in pianos, tuners make the octaves ever so slightly sharp and increasingly so in the upper range, and likewise modify the bass, but it is a very small effect. Find a grand piano, and pluck the individual strings. You will see. And there are no exceptions to this, either now or historically. Harpsichords had registers of single strings at 8 foot, 4 foot, and sometimes 16 foot pitch. A piano is not a harpsichord.
If you have questions about how pianos actually work you are welcome to contact me.
Most pianos are sampled, as the synthesis of the complexity across the compass is overwhelming. There are very successful piano models achieved with Physical Modelling technique, such as Pianoteq. Nearly indistingishable from a sampled instrument. The Sound on Sound article is very simplistic. Nevertheless interesting.