And there's also the Soul King palace being described as being in a separate dimension of Soul Society, so I'm not even sure that we can measure the "distance" in a straightforward manner.
https://i.imgur.com/Se3Ygpa.jpg
You wouldn't describe it as a separate dimension if it were just really, really, really far away. Rather, it's in an entirely separate space that you can't really assign a straightforward "distance" to.
How do you get from Seireitei to Soul King palace? Using a King's Key. But
what is a King's Key?
https://i.imgur.com/UIBeED9.png
The King's key is a power granted by the Soul King to division zero. If you have a King's Key, or alternatively, the power of the Soul King (which the King's key comes from), you can cross this dimension very easily. There's almost no mention of timeframe for people possessing an Ouken going from Seireitei to Soul King palace.
https://i.imgur.com/GG3FdWc.png
Although the heavenly pillar can traverse the distance,
it cannot reach the Spirit palace without a King's key.
How far does it travel to get to Soul King palace? Actually that's weird:
https://i.imgur.com/1egoyOv.png
https://i.imgur.com/MzMgyyo.png
2 pages later, with no mention or show of tremendous time or speed, they are instantly in the Soul King palace. Bleach almost always shows tremendous time or speed when they are present. But here there are almost instantly there.
Because they have a King's key with them.
To travel back, Ichigo, not having a King's key, was given an alternative, a special cloak made from a King's key.
But it operates differently. Rather than traverse the dimension with ease, it
forcefully breaks the barriers between dimensions in such a way that they remain open.
https://i.imgur.com/jPnRd6R.jpg
https://i.imgur.com/mYi0ghw.jpg
That is not at all how the division zero initially arrived.
https://i.imgur.com/Sm5RVYy.png
No mention of barriers being forced or remaining open - and it would of course be highly uncharacteristic of division zero to leave the Soul King vulnerable with no barrier at that point. No mention of travel time.
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So why does this matter?
Yhwach having absorbed / defeated the Soul King would have had the Soul King's ability to generate a King's key from will, which
allows him to pass anything from Soul Society to the Soul King palace with ease.
While there is some minimum distance that they have to travel - at least as high as Seireitei ++++ (and maybe a few times for measure) - the distance is nowhere near as massive as being sometimes suggested
if a King's key - the will of the Soul King or one of the guards - is present.
Everyone else feels a massive distance / barriers / etc that they must basically cheat with hax.
TLDR: You can assume dimensional weirdness in the elevation of the Wandenreich feat
if it makes it more consistent with other feats of his.