Consider an example like this:
var res = await Database.Query<Component>()
.IncludeMany(i => i.Labels)
.ToPageAsync(1, 1);
This returns one Component (as it should) but it also returns only the first label of that Component, even if there are more labels for that Component in the database. Looks to me like the paging logic is broken with .IncludeMany.
As a side-note: For Components without any Labels, NPoco seems to return Component.Labels=null, whereas Component.Labels=[] (empty array/collection) would be more appropriate IMHO.