The manouvers in my view had a clear focus on possible logistical support for and defence of the Russian enclave at Kaliningrad.
It makes plenty of military sense to practice that in times of growing tensions. In case of a hot war I think Russia would try to hold it, due to its location that makes it ideal to serve as a spearhead from which to spread a radar and SAM umbrella deep into NATO territory - the same what Washington wanted to do with the Crimean.