I don't know which School of Physics you went to Phil, but all routers are NOT the same despite radio power limits.
The Wi-Fi specification and legal requirement is a power maximum of 100mW transmit power. MIMO (see
https://en.wikipedia.org/wiki/MIMO) is about increasing the capacity of a signal to carry more data, it doesn't change how far a radio signal can propagate or what physical medium it can travel through, just how much data can be carried when the signal gets there.
If a thick stone wall is blocking all usable signal then at that point nothing else is going to help. The only way to get the signal to pass through is for the radio waves to hit the wall with more power. Two ways of doing this, either increase the transmit power, which isn't allowed, and even if it was or someone did this illegally, the TV will also need to break the legal requirements of Wi-Fi power levels and increase it's transmit power. The other alternative is to go from a roughly omni-directional antenna of a typical domestic Wi-Fi router to a very directional one, such as those used for long distances outdoors, this will concentrate all the 100mW into a narrow beam helping the signal reach the other side with enough usable power left, but again, you still have the problem of the TVs signal being received back, and the stone wall may still block it anyway.
As for review sites and testing methodologies, mostly tests about Wi-Fi (where everything else is the same, i.e. same Wi-Fi standard and features) are actually testing the Wi-Fi points radiation patterns (which all vary by design or by accident), this means a test seen online showing a good range and throughput doesn't necessarily translate to the same in a persons own home with the same kit, and vice versa. Unless the test uses very specialist equipment and good methodology, they should be treated as anecdotal, which basically applies to 99.9% of things seen on review sites and YouTube!
Regards
Phil