The "arming" is a little side effect of how the mechanism was developed, and my little theory is that it may or may not be observable depending on how the tolerances are set for each Zeitwerk. To understand that, we need to understand roughly how the movement works first...
If you want to see the arming occur on the movement side, have a look at this image (taken from Peter Chong's article of Zeitwerk):
This is the mechanism under the "anchor" steel bridge you see on the Zeitwerk movement.
Its hard to explain it simply (refer to diagram above), but the "green" colored disc is actually the seconds hand running. It has a little roller jewel on it that will rotate/push the Y-lever of the rementoir (it is slightly spring-loaded). Around 52 seconds in, it rotates the lever far enough that it "releases" a purple disc/cam. Note that in that 52 seconds, the rementoir spring has built up energy onto this purple disc/cam.
However, while that happens the Y-lever also drops another pallet jewel into the "gap" of another disc/cam (yellow). Note that both disc/cams are connected via gearing so they rotate together. This is the "priming" that occurs. Hence, if you observe your Zeitwerk movement side, look at the Y-bridge and observe the pallet jewel dropping into the yellow disc/cam. The "little priming jump" happens when that disc/cam rotates and gets blocked by the said pallet - and I believe how noticable the priming happens on the disc is depending on how these pallet jewels/discs are adjusted relative to each other.
At 60 seconds, the y-lever will be released by the running seconds hand and the Y-lever springs back into its original position via the spring, releasing that other disc. Now, both discs are free - it releases 60 seconds worth of rementoir spring energy to rotate the two discs simultaneously, which flips the minute/hour disc on the dial. The entire process then repeats for the next 60 seconds.
My theory is that the Rementoir is designed this way so that its easier for Lange to finely adjust the green seconds hand wheel+roller jewel and the Y-bridge to release exactly at 60 seconds. The other fine tolerance is to adjust the Y-bridge pallet jewels relative to the purple and yellow discs so they release/insert at the right moment at ~52 seconds in.
It could also be that since you have a newer Zeitwerk, that Lange might have "updated" or adjusted the tolerances differently. Refer to Point 3...
(Image also from Deployant @ Peter Chong)
For Question 3, all images I've seen of the Zeitwerk so far has the single piece bridge. I haven't seen any pictures of a separate bridge like yours, interesting! Do you have any other photos of it (e.g. at an angle)?