Cut and pasted from that most definitive of sources, Wikipedia......
According to the Wikipedia article, the claim to be the largest financial and business services centre outside London is based on 3 sources. Two of those are local Newspapers and the third is the very same website you've already posted a link for. As Manchester Kurt put it, none of those sources are exactly impartial.
So very much unproven. Although I suspect you will continue to believe whatever it suits you to believe.