50 extra Marines existing outside the formal structure of the Chapter organized into a strike force...wow quite a radical departure from the codex. Though it does make sense since Guilliman did mention he was going to make major revisions to the Codex Astartes.
Yep. The arrival of the Primaris is going to subvert a Chapter's Codex structure no matter what, either adding them to the companies brings them over 100 Space Marines, or forming new companies pushes them over ten in a Chapter. The Fulminata ("Thunderbolts") are a composite strike force outside the usual ten-company structure. I explore the impact all this change has on Ultramarine philosophy a bit, there's essentially a split between old and new, with a lot of the previous command echelons none too pleased with the new additions, which are understandably championed by the Primaris.