Then again, a lot of the transitions aren't finished yet either, and a lot of it is dependent on the final Deal or No Deal. It also takes time to do the groundwork if you want to move, like create the legal infrastructure and entities and the associated due diligence, rent office space, hire or relocate people, and so on.
So, it's too early yet to conclude anything in either direction, in my opinion.
[*] Hard to tell what is the true number of "high finance" employees in the UK. Given there are roughly 180K finance and insurance employees in the City of London, and most of the "high finance" is concentrated there, I'd guestimate 200-250K such "high finance" employees in the UK total, but I could be massively wrong. There are numbers putting the full time financial and insurance employees in the UK at 1.1M employees, but that includes bank tellers dealing with people wanting to buy a house and agents selling life insurance, etc.
It is a dirty city, housing is expensive and generally in a poor state, and there a lot of security issues and social unrest: burglaries, violent protests (almost every week), periodic riots in some suburbs and terrorist attacks. To the point that more and more in the media, you hear about an upcoming civil war. Add that all the famous France's plagues: strikes, bureaucracy, very high income taxes for people earning more than 2000/m Euros and more recently communities living more and more separately.
There is no social unrest in Germany, Frankfurt is much safer and Germany more reliable.
It is a solid 'upper middle' tier city, where everything is clean and neat.
What daily attractions does Paris have? Sure there is the Louvre but I didn't visit that as a tourist (no way I'm standing on these lines); so I don't think I'll be seeing it everyday to work.
It’s one of the downsides of Germany’s less centralized economy. While not the same status as London, Munich or Berlin would likely be more attractive destinations for their families.