Mine does the same on all of it. I suspect it's to placate the Greek elders (and have heard so from others), although they are slowly being replaced by non-Greek converts.
I do like the Greek in the service, though, but it can get kind of messy for newcomers and it changes randomly based on his feeling at the moment.
I also prefer "theion, ayion, achranton, athanaton, epouranion kai zopion, phrikton, &c." to "divine, holy, pure, immortal, heavenly, life-giving and tremendous, &c.", I just think that (where it is used) English should be integrated into the Liturgy in a sensible manner, not randomly.
For example, if the priest or deacon makes any exclamation in English, the response from the people should always be in English. So, "most especially for our most-holy, &c." should never elicit the response "axion estin os alithos, &c.". Likewise, when the Lord's prayer is said in Greek, the priest should not conclude the prayer with "for yours is the Kingdom, &c." in English.
Also, I don't see the logic in praying from "yper tis anothen eirinis, &c." to "yper pleonton, odhiporounton, &c." in Greek and then suddenly swapping to English at "for our delivery from all affliction, &c." and then swapping back to Greek at "tis panayias, achrantou, &c.".
I mean, what is the point of these practices? Is even a single person's attendance being guaranteed by this tokenistic sprinkling of English? Why bother at all?
And with that, I will refrain from hijacking this thread further ...