Get Sprite UVs in editor after calling SpriteAtlasUtility.PackAtlases

I'm writing an editor tool to allow dragging sprites between atlases to make the editing process easier.

The issue I'm having is after calling

SpriteAtlasUtility.PackAtlases(new[] { atlas }, EditorUserBuildSettings.activeBuildTarget);

when I later call spriteUvs = SpriteUtility.GetSpriteUVs(sprite, true);

I get a "System.ArgumentException: Could not get atlas data - Sprite is not packed" exception.

If I set the pack mode in the editor settings to "Always Enabled" and then enter play mode, after exiting play mode it will work as the atlases have been packed. T$$anonymous$$s is an issue as I just need to pack a single atlas or two at a time when editing them.

I've tried using the internal GetPreviewTextures method w$$anonymous$$ch works to get the atlas texture quickly, but there is no way to get the Sprite UVs from that.