About the other shards.

[Anonymoose]

For this kind of speculation, it's important to note that this difference is inherently relative.

Within each individual shard, time is passing at the same pace. However, due to the chaotic nature of the Rift, time is apparently "at different places" between shards relative to each other. This also oscillates. One shard might be "faster" than another at one point, and "slower" than that same shard later on. This was the case with the Source and the First, with them just "passing one another" and "catching up to each other' at this present moment. (How convenient for the plot!)

So if a shard is, right now, "ahead" of the Source, yeah, it might be more advanced. It might also be more advanced simply by virtue of existing just as long as us, but without having seven Calamities. Or perhaps it might be less advanced since the Ascians aren't meddling in their wars and inspiring technological breakthroughs!

TL;DR it's ALL on the table

[Jandor]

For this kind of speculation, it's important to note that this difference is inherently relative.

Within each individual shard, time is passing at the same pace. However, due to the chaotic nature of the Rift, time is apparently "at different places" between shards relative to each other. This also oscillates. One shard might be "faster" than another at one point, and "slower" than that same shard later on. This was the case with the Source and the First, with them just "passing one another" and "catching up to each other' at this present moment. (How convenient for the plot!)

I know they wanted the Scions to be established on the First, but I always wonder why they went for that particular excuse plot.

The jury rigged dimension hopping time travel tech being operated by a dude with terrible aim seems a far more convenient excuse.

Makes me wonder if the wobbly time stuff between shards is going to be relevant again at some point.

[Iscah]

The jury rigged dimension hopping time travel tech being operated by a dude with terrible aim seems a far more convenient excuse.

I think the idea might be that he'd already deliberately aimed wide by several months (by Source time) and then had the time dilation on top of that.

[Anonymoose]

I know they wanted the Scions to be established on the First, but I always wonder why they went for that particular excuse plot.

I think the big thing is that they needed what we saw in 3.4 to have taken place during the fall of the First, but also needed for enough time to have passed for the First to actually fall into a new status quo and not be mid-disaster. Almost everything we see on the First has a status quo that would take 100 years following the Flood of Light to establish. The wibbly wobbly timey wimey shenanigans helped establish more deeply-rooted fear and understanding of sin eaters, the entrenchment of the Light Wardens, the rise of Eulmoran culture, the raising of Crystarium, the politics of the fae realm, the conflicting sects of the religion of the Dark, the Warriors of Light becoming mythological villains rather than recently-living people who might be realistically understood, etc. Think about how much of the discussion with NPCs starts with, "Well, a hundred years ago..."

It was basically an excuse to make sure there was enough video game content and a new/interesting world setting.