Agreed, anything submitted, even if it fails gets put up.
I would say that they are "considering" an application and trying to gauge who will object, and maybe try and convince those people to give it the nod.
Or just trying to see if an application is even worth it.

As for the main question of devaluation etc.
I would say having a residential building not a commercial building at the end of the garden would increase value if indeed it did anything to the property value.
With regards to the actual works etc, that sadly is in the hands of the contractors, as we found out when the house next door to me eventually collapsed, threatening to take our house with it.

At this stage though, there is nothing to lose sleep over. Once an application actually gets submitted you will be able to see the actual plan, see how they wish to proceed, and object if you feel the need to do so.