Oh. I guess it's a Spine.ExposedList<Spine.Animation> now.
A Spine.ExposedList is the same as a System.Collections.Generic.List, except (1) the indexer was removed, and (2) element access is through the now-exposed internal array .Items
.
I'm not sure why this was done for the animation list, but for most cases in the runtime, this was to reduce the indexer overhead when processing large numbers of skeleton parts.
I guess given that, ToArray is the simplest way to do it.