Conditional region doing weird things to date picker form post data BUG?

I have a date picker within a conditional region (‘start_old’ as shown in image)
I also have a copy of the date picker ‘start’ outside the conditional region as the test control. (also shown in image)

The image below shows the payload after the form is fired on the second occasion.
It shows the data from the date picker ‘start_old’ repeated twice???
However on the first occasion, after browser reload, it does not show ‘start_old’ twice.

There is only one date picker in the form with the name start_old

The control date picker which is a duplicate of start_old but renamed (to ‘start’), is outside of the conditional region and does not exhibit the same behaviour:

image

Is this a bug??