LR Mobile uses Smart Previews that are 2560 on the longest side. This reduces cloud and local storage requirements but also precludes detailed analysis since you’re not seeing original pixel resolution.
I suppose that does save a lot of space, but disappointing nonetheless. For me, that would reduce the app's practical functionality to simple browsing ...
Why is it disappointing? It isn't a secret as it is a well-published spec. The size of the Smart Preview used exceeds the display resolution of the state-of-the-art IOS device.
I know ~nothing about Lightroom mobile.
That said, if it's getting the smart previews from Lightroom, you can make those any size you want.
For example, using a script I wrote (free) called 'Rebuild Smart Previews' (any size you want).
It's possible that something might not like those being non-standard size, but I've not run into it, yet.
Rikk writes: "... The size of the Smart Preview used exceeds the display resolution of the state-of-the-art IOS device."
It exceeds the screen resolution for most monitors! Does that keep you from evaluating noise/detail?
If you want to zoom in to true 1:1 for best detail evaluation, then you need full-rez smart previews.