Improve migration guide

docs/content/reference/migration/migration-0-18.md

@@ -82,9 +82,12 @@ For this purpose `TranslationRotationScale3D` and `TranslationAndMat3x3` datatyp
    * this replaces the previous `from_parent` bool
    * `from_parent` is still available in all SDK languages, but deprecated
 
-All components are applied to the final transform in the opposite order they're listed in. E.g. if both a 4x4 matrix and a translation is set, the entity is first translated and then transformed with the matrix.
+All components are applied to the final transform in the opposite order they're listed in. E.g. if both a 3x3 matrix and a translation is set, the entity is first translated and then transformed with the matrix.
 If translation, rotation & scale are applied, then (just as in prior versions), from the point of view of the parent space the object is first scaled, then rotated and then translated.
 
+When you log the `Transform3D` archetype, _all_ components are written, even if you don't set them.
+This means that if you first log a `Transform3D` with a `Translation3D` and then later another `Transform3D` with a `RotationQuat`, this will result in an entity that is only rotated.
+
 Other changes in data representation:
 * Scaling no longer distinguishes uniform and 3D scaling in its data representation, it is now always expressed as 3 floats with the same value. Helper functions are provided to build uniform scales.
 * Angles (as used in `RotationAxisAngle`) are now always stored in radians, conversion functions for degrees are provided.