I posted "which does not fully agree with what you have"

So, is my last statement true?

I suspect that this 'unorthodox' mode that I have never heard used except when T1 is UART timer will differ slightly from derivative to derivative if T1 is used for anything else. I can see a chip designer saying "let us just make T0 mode 3 work with T1 UART timer, and ignore other T1 uses with T0 M3, nobody will ever find out"

I have no such knowledge, but your question made me curious and, while they may work the same, the description of T0 M3 for a few derivatives I checked vary.

Erik