for collections, the elements will appear (as the collection has the elements inside it), but it will also show you the other internal elements (useful to debug lazy collections for instance).
Thus, compared to the Doctrine dumper, it will not initialize lazy collection as a side effect of debugging them.

Note that the code available on Moday was including a caster for Doctrine Collection, but @nicolas-grekas and I decided to remove it when discussing about it during the hackday yesterday because of the reason above.