It’s wild they talk about the jitter in the pps signals but glossed over the jitter the oscilloscope?
It appears to be set to trigger on the bottom trace (it appears still) and then retrospectively display the other two.
For anything that involves a scope, I think it's good practice to specify how and what you are measuring - namely what termination, what trigger level and show what the pulse actually looks like on the scope.
Where you are definitely right is that all those devices can produce completely different looking pulses, and only by looking at the pulse with a scope that has sufficient bandwidth you can pick the right trigger level that lands at a point of the waveforms that gets consistent characteristics, namely you stay away from the top of the pulse and tend to trigger somewhere mid-ramp that looks clean, and keep your paws away from those AUTO buttons!
...but this is all nitpicking as far as the post goes, this is where lots of electronics people get triggered (badum, tss!) where we have a network in the middle that is, essentially, chaos.
Uh, the Siglent SDS 1204X-E used here has a "new, innovative digital trigger with low latency" ...
But yes, as others have commented already, if only the relative jitter between the signals is of interest, the trigger jitter itself is inconsequential.
Datasheet claims trigger jitter of <100 ps.