Is it wanted?
Usually a choice type gives you the ability to chose between a set a pre-defined values. A collection is preferred for your use case.
Please send support requests to the symfony mailing list, thanks
In fact it can't works with a collectionType as each item of a collection has a different name.
For example, if I create a collection of radioType, I would be able to check all the radio buttons of the collection.
In my mind it was a feature request rather than a support request. Sorry for the inconvenience.