Conceeded. I cannot quote a primary source; I was repeating an observation of a friend who is himself leading a start up.
I say your friend is indeed closer to the truth.
There are a shed load of tech companies around the area and wider area within a ten minute walk, I would estimate that there are thousands. I know because I have an office there, work the area, have customers there. There's probably 150 on Great Eastern St alone, just figure out the amount of office space in the vicinity and 150 doesn't scratch the surface.
150 may refer to "Industry names" and not take in to account businesses like mine that support these companies.
There are lots of council / ex-council blocks either side of Old street, plenty of private flats as well where WG's operate from.
Any office in the city (EC) is a max of 15 minutes walk from Old St.
Old st has good transport links.
What's not to like for a WG?