Just because the reason behind practice X is Y doesn't mean Y is also the reason for another practice Z, I don't think... (On a side note, I'm not sure if the rationale for editorial "we" is what you seem to suggest it is. See en.wikipedia.org/wiki/We#The_author.27s_.22we.22 )

If he wanted to come across as obnoxious, he should have thanked for their continuous 22 years of support since he was born to eliminate other possibilities (e.g., the parents may have adopted him).