That's basically correct. There is a certain item rating level that once an individual item slot goes over that rating, it starts only getting expertise for its bolster (no more "PvE" stats). As the item rating continues to rise, you get less and less expertise until eventually bolster doesn't get anything from that item. The result should be that in the best PvE gear, you are somewhere between the "introduction bolster" level and the top end PvP gear in power. You would still be better off swapping to PvP gear if you have it, but you aren't terrible.
That sounds very interesting. I wonder how that will work with high end PVE gear. Does it mean that the better the item is, the less expertise it will receive from bolster? Maybe a better approach would be bolstering everyone to equal expertise level, but reducing their PVE stats based on the amount of bolster received?
Also worth pointing out that this system works on an individual item basis, so each slot itself is bolstered up independently of all of the other slots on a character, so slots can give more of a bolster bonus than others if you have a really powerful item in your chest slot, as an example, but a really behind the curve implant.