Whether the GIRM is clear or not isn’t necessarily the point. It does seem to say in Paragraph 42 that we should stand while the priest says ‘Pray Brethren…’; however, in the very next paragraph it says…
*But **it is up to the Conference of Bishops to adapt the gestures and posture in the Order of the Mass *to the customs and reasonable traditions of the people according to the norm of law…
And that seems to be what the Bishops are doing in the BCL newsletter. Now that being said, it’s even more confusing when you read the next paragraph of the GIRM. It says…
For the sake of observing a uniformity in gestures and* posture during the same celebration,** the faithful should obey the directions which the deacon or a lay person or the priest** give during the celebration, according to whatever is indicated in the liturgical books. *
…So the confusion really seems to be whether we follow the clarification in the BCL Newsletter, OR for the sake of unity, we do whatever that particular parish is doing? I tend to agree with the previous post asking why they fixed this when it wasn’t broken. It seems to have actually made the situation far worse. For my part, I follow what’s in the BCL newsletter as being what the Bishop’s intended.