As in most collisions I believe the blame will be shared, for sure, both HI and Sola TS could had done more to avoid collision.
The expression navigational exercise can mean a lot of things, apparently the AIS was of on HI, what instruments (lights, radar, etc…) that was on we don’t know, I have sailed on tankers with Captains that didn’t like to use the radar too much(before GPS and AIS).
All communication from Sola TS to third parties was in Norwegian although for sure none of the other parts of the bridge-team understood Norwegian. I have myself (Norwegian) many times been at the terminal, and all navigational talk were done in english, only chit chat not related to the safe navigation of the ship was done in Norwegian.