Nested fields & strict dynamic mapping

Hello,
Following this stackoverlow question, i came here before opening an issue on github.

An indice with the following mapping:

{
   "test2": {
      "mappings": {
         "dynamic": "strict",
         "properties": {
            "field1": {
               "properties": {
                  "field2": {
                     "type": "text"
}}}}}}} // collapsed

Accepts updates and indexes such as the following :

POST /test2/_doc/0
{
   "doc": {
      "field1.field2": "1"
}}

Which would be fine if the resulting document's _source were :

"field1": {
  "field2": "1"
}

But the resulting document's _source is :

"field1.field2": "1"

In other words, is seems to me that despite the "dynamic": "strict" mapping parameter, a new field "field1.field2" is added.
It has to be noted however, that the mapping does stay exactly the same.

Edit : updating the document with different values for the "field1.field2" and "field1": {"field2"} results in different values for each.