Do not mix the exclusive economical zone (EEZ, 200 NM) and the sovereign area. The aircraft has been in the EEZ, not in the sovereign area (12 NM) of the Russian Federation.
Yes the aircraft crossed the border of the Russian Federation EEZ. The EEZ extends up to 200 NM from the coastline (even further if there is a continental shelf continuity; Russian Federation tried to use this possibility to extend its EEZ up to the Svalbard archipelago, but it's now resolved).
However the airspace over the EEZ is not a sovereign airspace, in fact its entirely free for aircraft.
Sovereign airspace definition
Sovereignty over airspace is limited to 12 NM from the coastline according to Chicago and UNCLOS conventions. UNCLOS defines the limit of the territorial seas, and the Chicago convention states the airspace over territorial seas is sovereign:
Obviously the flight path is not close to this limit at any time.
ADIZ, need to be identified
Unlike the US, the Russian Federation has no official air defense identification zones (the ADIZ concept, which is not part of any international treaty). It means overflying aircraft have no obligation to identify themselves unless they want to enter the sovereign airspace.
EEZ vs sovereign airspace confusion
The EEZ defines important economic rights for activities from the sea surface. However UNCLOS does not grant any right on the airspace over the EEZ (art. 57, 58 and 78). In particular the EEZ adds no restriction for overflying, aircraft are granted all of the rights defined for high sea areas (the seas beyond the EEZ). E.g.:
In the exclusive economic zone, all States, whether coastal or
land-locked, enjoy, subject to the relevant provisions of this Convention, the freedoms referred to in article 87 of navigation and overflight and of the laying of submarine cables and pipelines, and other internationally lawful uses of the sea [...]
This confusion seems to be pervasive in the media which often report the "violation" of Taiwanese airspace by China, while these flights are entirely lawful in the EEZ (ignoring the ADIZ which is another topic) as long as the 12 NM national airspace is respected (assuming Taiwan is sovereign, which is indeed disputed).