Yes, it was Bishop Nikolai. In that Archbishop Demetrios is the locum tenens of ACROD and was the presiding hierarch at the funeral services, it is obvious that the Bishop is not under any ecclesiastical sanction that would have prohibited his participation.
I was present at St. John's over the weekend. Bishop Nikolai was of student of Metropolitan Nicholas when the late Metropolitan was prefect of Christ the Saviour Seminary in Johnstown, PA and Bishop Nikolai was a student. He came to pay his respects and honor his teacher. I was introduced to him and he was polite and appeared to be very low key and he acted with appropriate humility. It was the first time I saw him since he was a Seminarian in the 1960's.
For those who were inquiring about his health here last week, the Bishop gave a brief eulogy on Sunday after offering a Panachida in which he noted that both he and the late Metropolitan had suffered from the same form of cancer, but that he, Bishop Nikolai, was doing well.