In old UI framework:

When multivalue is configured with DelegatingMultiValueSubnodeTransformer, subnodes are saved as indexes (0, 1, 2, ...)

In new UI framework:

Multivalue field name is always prepend before the index, for example (allVehicles0, allVehicles1, ...)

The use case for having just indexes as names comes from content-type apps, where DelegatingMultiValueSubnodeTransformer is used to save multivalue fields.

New UI framework uses resolution strategy to find children of multivalue fields. The strategy ByIndexedChildNodes always prepends the node name.