Bob, I really enjoy your writings, always have since I first read some in the early 2000's......i find you provoke positive questioning in my mind and hopefully in the minds of others.
Now I'm not absolutely confident about the relative pressures produced by roots under rigid slabs, so I will defer to the values you suggest, however clearly in the pics posted and in almost all the anecdotal experiences i have had with roots its dynamic leverage vs inflexible, flat concrete sheets lying over poorly prepared foundation layers.
It would be very hard to calculate just what pressures are being produced by the mass of roots that you would find under such slabs/sheets. But...what I would be confident in stating is that given a crow bar I could get movement in those slabs...the slads would probably crack at the point of leverage...the mass of roots have an advatage of spreading the loading...very clear in Erics 2nd pic...if you tried to lever up the slad at the red arrow it would crack but the proposed spread of lifting root mass (yellow lines) combined with the heaving of the soil beneath has little trouble moving the slab/sheet, and this does not surprise me at all.
The claims that are made against trees in relation to building foundations, are a different thing entirely, and I have written at some length about this on the forum previously....differential settlement of the subbase is very often the real cause for subsidence under buildings....correct foundation preparationand construction eliminates the direct physical role of roots.....moisture changes in the soil surrounding and below the foundation is effected by all vegetation but again correct foundations are not as vulnerable as the commonly held view suggests.