Apart from the fact that I've never read such books you're totally right, but only a single post later you write "a combat team of MBTs vs. a battalion+ of light tanks". Such a scenario is as unrealistic as a one-on-one standoff. An Army that can only bring a couple of MBT's into the battle vs a batallion sized enemy wouldn't have performed any better if it had Light Tanks instead. Such a statement is worthless when evaluating the performance of MBTs vs Light Tanks. That's more of a criticism toward the logistical abilities of that particular Armed Forces.
Perhaps I haven’t fully explained what I mean here in relation to 10 vs 40. I used the term concentrate and thought that would be enough. It has nothing to do with overall numbers of logistics but how many vehicles you can manoeuvre in response to the enemy to achieve concentration.
In analysing the effectiveness of light tanks vs MBTs one has to do so from a systems perspective. In particular analysing the difference between the RDF/LT and a LAV based gun platform (like the Stryker MGS) versus the M1 one finds that in conventional open terrain tank vs tank fighting the lighter tanks have a range of advantages. In particular higher mobility allowing the commander to concentrate more force when and where its needed.
Assume you have a US armoured cavalry regiment defending against a Soviet tank division. Once you identify the Soviet axes of advance you concentrate your tanks to meet and engage them. With a formation of M1 tanks you can only concentrate a single company or combat team of tanks but with the faster moving lighter tanks you can concentrate an entire ‘squadron’ or battle group. This provides you the 40 vs 10 advantage.
It is important to note that mobility isn’t just some maximum speed listed in Janes but actual deployable speed of an entire tank company. In this case the light tank has significant advantages over most terrain types than the M1. Helicopter supported light tanks have even more significant mobility advantages. Imagine trying to move a convoy of 20 buses from one town to the next through some back streets and country tracks. Then imagine trying to move a convoy of 20 Smart cars over the same route. Maximum speed may not be very different but the ease in which the smaller cars can formate and manoeuvre gives them a clear advantage.
Or use the Somali example. The 2 Delta Force snipers will beat the 1,000 Somalis if the Somalis can't concentrate their force. If they are limited by their own mobility and terrain to only approach the snipers 10 men at a time then the snipers will win. However if they can concentrate and approach at 100 a time they will have overwhelming firepower.
This is why in any kind of battle simulation and often in the real world (Israeli Shermans and AM-13s thumping Egyptian JS-3s and T-55s) lighter vehicles that have faster ‘operational’ mobility win out. This is what motivated the West to move down the LAV path in the 90s for FCS and FRES. Unfortunately the real world intervened and enemy forces facing dominant western air-land firepower have retreated into close terrain like cityscapes where armour counts for more than mobility.