This is only my own opinion mind but......
He had no need to mention it. He was there as a coach, not a referee. It was a case of one-upmanship on his part and nothing more.
He might as well have said "Oh and by the way mate, because I happen to be a Level 5 ref and assessor, it more than likely means that any decision you make that I contest or disagree with from the sidelines - you're probably wrong and it should probably undermine your authority and/or confidence - no pressure"......
Any smug coach who tells me he's a ref and assessor before a match will get the stock response from me:
"Not today you're not mate - you're a coach".
Besides, he may have been bullshitting anyway. No way of knowing......