Nope, not JP Morgan, although I did interview with them too and they talked about some of their Python systems and how they were currently in the process of porting to Python 3.
I won't name names, but they're also in the top ten and based in America.
The platform can already run in python 3. It's possible that the team you interviewed with wasn't aware of that.
Like all big companies, personal experience varies with the team and the part of the company you're in.