Hi, this was a simplification in the code of the "Export Parameters" dialog, to handle generic parameters of any node.
Internally, all parameters are defined by its type (integer, float, etc) and can be "single" or "triple". But it doesn't difference between XYZ or UVW... both are triple floats.
We'll see if it can be fixed, without too much changes. If not, we'll add a note to the documentation.
Thanks for reporting it.