I ran into similar arguments among Catholics, which is actually (I think) what prompted me to dig deeper into this area. I would sit in chats, and Protestants would come in, and the Catholics would start launching all sorts of arguments about the Bible being fixed by them and whatnot, and when I would point out that the EO have a different Bible, as do others, and that their arguments might be a bit overstated, they normally just ignored me. Unfortunately, I got a bit riled up and ended up trying to go the other direction, and dogmatizing the fact that the Scripture isn't really (universally binding) dogma.
Anyway, regarding St. John Chrysostom, the quote I was thinking of is not an actual canonical list, but rather something he said in the middle of a sermon. He was rebuking his flock for not reading their Bibles but instead focusing on worldly things. Then, he says something which implies that there is a set canon, and that people shouldn't have any question about what constitutes that canon:
Is it not strange that those who sit by the market can tell the names, and families, and cities of charioteers, and dancers, and the kinds of power possessed by each, and can give exact account of the good or bad qualities of the very horses, but that those who come hither should know nothing of what is done here, but should be ignorant of the number even of the sacred Books? - Homily 32 on John
Regarding the quote from St. Gregory the Theologian, he does mention a Scriptural canon:
Be not disposed to treat books with the mind of thief, For there are many pieces of viciousness interpolated therein. Accept this number, my friend, from me as the approved list... [St. Gregory then goes on to give a list that excludes the deuterocanonical books] ...If any be found outside of these, they are not genuine. - Canon of St. Gregory the Theologian
This quote from St. Gregory is included in the EOC's canonical tradition. St. John and St. Gregory do seem to quote from the Apocrypha in their writings, but I get the feeling that they don't realise who they are quoting (I have observed this among many prominent Fathers). Other Fathers do quote the deuterocanonicals by name, as Scripture though. Unfortunately, I can't think of any early Fathers that came out and said that the canon of Scripture was not dogma.