Timing is very good generally, giving due weight to commas, quotations, etc. But at the end of a sentence the final period doesn't contribute any pause at all. That is, the period at the end of each sentence is hurried over with no discernable pause. Copying the text to Text Edit and asking Mac OS to read it works fine - that is, periods are honoured and generate suitable pauses.
Thus, the problem is not with Mac OS, but probably with the way that Logos is passing text to Mac OS's speech engine to be read aloud.
Read aloud is very useful to help keep my mind focused on the text as I follow along with the reading - please can this (admittedly little) issue be fixed?